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passt/tcp.c
David Gibson 1a40d00895 port_fwd: Split TCP and UDP cases for get_bound_ports() 
Currently get_bound_ports() takes a parameter to determine if it scans for
UDP or TCP bound ports, but in fact there's almost nothing in common
between those two paths.  The parameter appears primarily to have been
a convenience for when we needed to invoke this function via NS_CALL().

Now that we don't need that, split it into separate TCP and UDP versions.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
2023-11-07 09:53:26 +01:00

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// SPDX-License-Identifier: GPL-2.0-or-later
/* PASST - Plug A Simple Socket Transport
* for qemu/UNIX domain socket mode
*
* PASTA - Pack A Subtle Tap Abstraction
* for network namespace/tap device mode
*
* tcp.c - TCP L2-L4 translation state machine
*
* Copyright (c) 2020-2022 Red Hat GmbH
* Author: Stefano Brivio <sbrivio@redhat.com>
*/
/**
* DOC: Theory of Operation
*
*
* PASST mode
* ==========
*
* This implementation maps TCP traffic between a single L2 interface (tap) and
* native TCP (L4) sockets, mimicking and reproducing as closely as possible the
* inferred behaviour of applications running on a guest, connected via said L2
* interface. Four connection flows are supported:
* - from the local host to the guest behind the tap interface:
* - this is the main use case for proxies in service meshes
* - we bind to configured local ports, and relay traffic between L4 sockets
* with local endpoints and the L2 interface
* - from remote hosts to the guest behind the tap interface:
* - this might be needed for services that need to be addressed directly,
* and typically configured with special port forwarding rules (which are
* not needed here)
* - we also relay traffic between L4 sockets with remote endpoints and the L2
* interface
* - from the guest to the local host:
* - this is not observed in practice, but implemented for completeness and
* transparency
* - from the guest to external hosts:
* - this might be needed for applications running on the guest that need to
* directly access internet services (e.g. NTP)
*
* Relevant goals are:
* - transparency: sockets need to behave as if guest applications were running
* directly on the host. This is achieved by:
* - avoiding port and address translations whenever possible
* - mirroring TCP dynamics by observation of socket parameters (TCP_INFO
* socket option) and TCP headers of packets coming from the tap interface,
* reapplying those parameters in both flow directions (including TCP_MSS,
* TCP_WINDOW_CLAMP socket options)
* - simplicity: only a small subset of TCP logic is implemented here and
* delegated as much as possible to the TCP implementations of guest and host
* kernel. This is achieved by:
* - avoiding a complete TCP stack reimplementation, with a modified TCP state
* machine focused on the translation of observed events instead
* - mirroring TCP dynamics as described above and hence avoiding the need for
* segmentation, explicit queueing, and reassembly of segments
* - security:
* - no dynamic memory allocation is performed
* - TODO: synflood protection
*
* Portability is limited by usage of Linux-specific socket options.
*
*
* Limits
* ------
*
* To avoid the need for dynamic memory allocation, a maximum, reasonable amount
* of connections is defined by TCP_MAX_CONNS (currently 128k).
*
* Data needs to linger on sockets as long as it's not acknowledged by the
* guest, and is read using MSG_PEEK into preallocated static buffers sized
* to the maximum supported window, 16 MiB ("discard" buffer, for already-sent
* data) plus a number of maximum-MSS-sized buffers. This imposes a practical
* limitation on window scaling, that is, the maximum factor is 256. Larger
* factors will be accepted, but resulting, larger values are never advertised
* to the other side, and not used while queueing data.
*
*
* Ports
* -----
*
* To avoid the need for ad-hoc configuration of port forwarding or allowed
* ports, listening sockets can be opened and bound to all unbound ports on the
* host, as far as process capabilities allow. This service needs to be started
* after any application proxy that needs to bind to local ports. Mapped ports
* can also be configured explicitly.
*
* No port translation is needed for connections initiated remotely or by the
* local host: source port from socket is reused while establishing connections
* to the guest.
*
* For connections initiated by the guest, it's not possible to force the same
* source port as connections are established by the host kernel: that's the
* only port translation needed.
*
*
* Connection tracking and storage
* -------------------------------
*
* Connections are tracked by struct tcp_tap_conn entries in the @tc
* array, containing addresses, ports, TCP states and parameters. This
* is statically allocated and indexed by an arbitrary connection
* number. The array is compacted whenever a connection is closed, by
* remapping the highest connection index in use to the one freed up.
*
* References used for the epoll interface report the connection index used for
* the @tc array.
*
* IPv4 addresses are stored as IPv4-mapped IPv6 addresses to avoid the need for
* separate data structures depending on the protocol version.
*
* - Inbound connection requests (to the guest) are mapped using the triple
* < source IP address, source port, destination port >
* - Outbound connection requests (from the guest) are mapped using the triple
* < destination IP address, destination port, source port >
* where the source port is the one used by the guest, not the one used by the
* corresponding host socket
*
*
* Initialisation
* --------------
*
* Up to 2^15 + 2^14 listening sockets (excluding ephemeral ports, repeated for
* IPv4 and IPv6) can be opened and bound to wildcard addresses. Some will fail
* to bind (for low ports, or ports already bound, e.g. by a proxy). These are
* added to the epoll list, with no separate storage.
*
*
* Events and states
* -----------------
*
* Instead of tracking connection states using a state machine, connection
* events are used to determine state and actions for a given connection. This
* makes the implementation simpler as most of the relevant tasks deal with
* reactions to events, rather than state-associated actions. For user
* convenience, approximate states are mapped in logs from events by
* @tcp_state_str.
*
* The events are:
*
* - SOCK_ACCEPTED connection accepted from socket, SYN sent to tap/guest
*
* - TAP_SYN_RCVD tap/guest initiated connection, SYN received
*
* - TAP_SYN_ACK_SENT SYN, ACK sent to tap/guest, valid for TAP_SYN_RCVD only
*
* - ESTABLISHED connection established, the following events are valid:
*
* - SOCK_FIN_RCVD FIN (EPOLLRDHUP) received from socket
*
* - SOCK_FIN_SENT FIN (write shutdown) sent to socket
*
* - TAP_FIN_RCVD FIN received from tap/guest
*
* - TAP_FIN_SENT FIN sent to tap/guest
*
* - TAP_FIN_ACKED ACK to FIN seen from tap/guest
*
* Setting any event in CONN_STATE_BITS (SOCK_ACCEPTED, TAP_SYN_RCVD,
* ESTABLISHED) clears all the other events, as those represent the fundamental
* connection states. No events (events == CLOSED) means the connection is
* closed.
*
* Connection setup
* ----------------
*
* - inbound connection (from socket to guest): on accept() from listening
* socket, the new socket is mapped in connection tracking table, and
* three-way handshake initiated towards the guest, advertising MSS and window
* size and scaling from socket parameters
* - outbound connection (from guest to socket): on SYN segment from guest, a
* new socket is created and mapped in connection tracking table, setting
* MSS and window clamping from header and option of the observed SYN segment
*
*
* Aging and timeout
* -----------------
*
* Timeouts are implemented by means of timerfd timers, set based on flags:
*
* - SYN_TIMEOUT: if no ACK is received from tap/guest during handshake (flag
* ACK_FROM_TAP_DUE without ESTABLISHED event) within this time, reset the
* connection
*
* - ACK_TIMEOUT: if no ACK segment was received from tap/guest, after sending
* data (flag ACK_FROM_TAP_DUE with ESTABLISHED event), re-send data from the
* socket and reset sequence to what was acknowledged. If this persists for
* more than TCP_MAX_RETRANS times in a row, reset the connection
*
* - FIN_TIMEOUT: if a FIN segment was sent to tap/guest (flag ACK_FROM_TAP_DUE
* with TAP_FIN_SENT event), and no ACK is received within this time, reset
* the connection
*
* - FIN_TIMEOUT: if a FIN segment was acknowledged by tap/guest and a FIN
* segment (write shutdown) was sent via socket (events SOCK_FIN_SENT and
* TAP_FIN_ACKED), but no socket activity is detected from the socket within
* this time, reset the connection
*
* - ACT_TIMEOUT, in the presence of any event: if no activity is detected on
* either side, the connection is reset
*
* - ACK_INTERVAL elapsed after data segment received from tap without having
* sent an ACK segment, or zero-sized window advertised to tap/guest (flag
* ACK_TO_TAP_DUE): forcibly check if an ACK segment can be sent
*
*
* Summary of data flows (with ESTABLISHED event)
* ----------------------------------------------
*
* @seq_to_tap: next sequence for packets to tap/guest
* @seq_ack_from_tap: last ACK number received from tap/guest
* @seq_from_tap: next sequence for packets from tap/guest (expected)
* @seq_ack_to_tap: last ACK number sent to tap/guest
*
* @seq_init_from_tap: initial sequence number from tap/guest
* @seq_init_to_tap: initial sequence number from tap/guest
*
* @wnd_from_tap: last window size received from tap, never scaled
* @wnd_from_tap: last window size advertised from tap, never scaled
*
* - from socket to tap/guest:
* - on new data from socket:
* - peek into buffer
* - send data to tap/guest:
* - starting at offset (@seq_to_tap - @seq_ack_from_tap)
* - in MSS-sized segments
* - increasing @seq_to_tap at each segment
* - up to window (until @seq_to_tap - @seq_ack_from_tap <= @wnd_from_tap)
* - on read error, send RST to tap/guest, close socket
* - on zero read, send FIN to tap/guest, set TAP_FIN_SENT
* - on ACK from tap/guest:
* - set @ts_ack_from_tap
* - check if it's the second duplicated ACK
* - consume buffer by difference between new ack_seq and @seq_ack_from_tap
* - update @seq_ack_from_tap from ack_seq in header
* - on two duplicated ACKs, reset @seq_to_tap to @seq_ack_from_tap, and
* resend with steps listed above
* - set TCP_WINDOW_CLAMP from TCP header from tap
*
* - from tap/guest to socket:
* - on packet from tap/guest:
* - set @ts_tap_act
* - set TCP_WINDOW_CLAMP from TCP header from tap
* - check seq from header against @seq_from_tap, if data is missing, send
* two ACKs with number @seq_ack_to_tap, discard packet
* - otherwise queue data to socket, set @seq_from_tap to seq from header
* plus payload length
* - in ESTABLISHED state, send ACK to tap as soon as we queue to the
* socket. In other states, query socket for TCP_INFO, set
* @seq_ack_to_tap to (tcpi_bytes_acked + @seq_init_from_tap) % 2^32 and
* send ACK to tap/guest
*
*
* PASTA mode
* ==========
*
* For traffic directed to TCP ports configured for mapping to the tuntap device
* in the namespace, and for non-local traffic coming from the tuntap device,
* the implementation is identical as the PASST mode described in the previous
* section.
*
* For local traffic directed to TCP ports configured for direct mapping between
* namespaces, see the implementation in tcp_splice.c.
*/
#include <sched.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <signal.h>
#include <stdlib.h>
#include <errno.h>
#include <limits.h>
#include <net/ethernet.h>
#include <net/if.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <stdint.h>
#include <stdbool.h>
#include <stddef.h>
#include <string.h>
#include <sys/epoll.h>
#ifdef HAS_GETRANDOM
#include <sys/random.h>
#endif
#include <sys/socket.h>
#include <sys/timerfd.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <time.h>
#include <linux/tcp.h> /* For struct tcp_info */
#include "checksum.h"
#include "util.h"
#include "passt.h"
#include "tap.h"
#include "siphash.h"
#include "pcap.h"
#include "tcp_splice.h"
#include "log.h"
#include "inany.h"
#include "tcp_conn.h"
#define TCP_FRAMES_MEM 128
#define TCP_FRAMES \
(c->mode == MODE_PASST ? TCP_FRAMES_MEM : 1)
#define TCP_HASH_TABLE_LOAD 70 /* % */
#define TCP_HASH_TABLE_SIZE (TCP_MAX_CONNS * 100 / \
TCP_HASH_TABLE_LOAD)
#define MAX_WS 8
#define MAX_WINDOW (1 << (16 + (MAX_WS)))
/* MSS rounding: see SET_MSS() */
#define MSS_DEFAULT 536
struct tcp4_l2_head { /* For MSS4 macro: keep in sync with tcp4_l2_buf_t */
#ifdef __AVX2__
uint8_t pad[26];
#else
uint8_t pad[2];
#endif
struct tap_hdr taph;
struct iphdr iph;
struct tcphdr th;
#ifdef __AVX2__
} __attribute__ ((packed, aligned(32)));
#else
} __attribute__ ((packed, aligned(__alignof__(unsigned int))));
#endif
struct tcp6_l2_head { /* For MSS6 macro: keep in sync with tcp6_l2_buf_t */
#ifdef __AVX2__
uint8_t pad[14];
#else
uint8_t pad[2];
#endif
struct tap_hdr taph;
struct ipv6hdr ip6h;
struct tcphdr th;
#ifdef __AVX2__
} __attribute__ ((packed, aligned(32)));
#else
} __attribute__ ((packed, aligned(__alignof__(unsigned int))));
#endif
#define MSS4 ROUND_DOWN(USHRT_MAX - sizeof(struct tcp4_l2_head), 4)
#define MSS6 ROUND_DOWN(USHRT_MAX - sizeof(struct tcp6_l2_head), 4)
#define WINDOW_DEFAULT 14600 /* RFC 6928 */
#ifdef HAS_SND_WND
# define KERNEL_REPORTS_SND_WND(c) (c->tcp.kernel_snd_wnd)
#else
# define KERNEL_REPORTS_SND_WND(c) (0 && (c))
#endif
#define ACK_INTERVAL 10 /* ms */
#define SYN_TIMEOUT 10 /* s */
#define ACK_TIMEOUT 2
#define FIN_TIMEOUT 60
#define ACT_TIMEOUT 7200
#define LOW_RTT_TABLE_SIZE 8
#define LOW_RTT_THRESHOLD 10 /* us */
/* We need to include <linux/tcp.h> for tcpi_bytes_acked, instead of
* <netinet/tcp.h>, but that doesn't include a definition for SOL_TCP
*/
#define SOL_TCP IPPROTO_TCP
#define SEQ_LE(a, b) ((b) - (a) < MAX_WINDOW)
#define SEQ_LT(a, b) ((b) - (a) - 1 < MAX_WINDOW)
#define SEQ_GE(a, b) ((a) - (b) < MAX_WINDOW)
#define SEQ_GT(a, b) ((a) - (b) - 1 < MAX_WINDOW)
#define FIN (1 << 0)
#define SYN (1 << 1)
#define RST (1 << 2)
#define ACK (1 << 4)
/* Flags for internal usage */
#define DUP_ACK (1 << 5)
#define ACK_IF_NEEDED 0 /* See tcp_send_flag() */
#define OPT_EOL 0
#define OPT_NOP 1
#define OPT_MSS 2
#define OPT_MSS_LEN 4
#define OPT_WS 3
#define OPT_WS_LEN 3
#define OPT_SACKP 4
#define OPT_SACK 5
#define OPT_TS 8
#define CONN_V4(conn) (!!inany_v4(&(conn)->faddr))
#define CONN_V6(conn) (!CONN_V4(conn))
#define CONN_IS_CLOSING(conn) \
((conn->events & ESTABLISHED) && \
(conn->events & (SOCK_FIN_RCVD | TAP_FIN_RCVD)))
#define CONN_HAS(conn, set) ((conn->events & (set)) == (set))
static const char *tcp_event_str[] __attribute((__unused__)) = {
"SOCK_ACCEPTED", "TAP_SYN_RCVD", "ESTABLISHED", "TAP_SYN_ACK_SENT",
"SOCK_FIN_RCVD", "SOCK_FIN_SENT", "TAP_FIN_RCVD", "TAP_FIN_SENT",
"TAP_FIN_ACKED",
};
static const char *tcp_state_str[] __attribute((__unused__)) = {
"SYN_RCVD", "SYN_SENT", "ESTABLISHED",
"SYN_RCVD", /* approximately maps to TAP_SYN_ACK_SENT */
/* Passive close: */
"CLOSE_WAIT", "CLOSE_WAIT", "LAST_ACK", "LAST_ACK", "LAST_ACK",
/* Active close (+5): */
"CLOSING", "FIN_WAIT_1", "FIN_WAIT_1", "FIN_WAIT_2", "TIME_WAIT",
};
static const char *tcp_flag_str[] __attribute((__unused__)) = {
"STALLED", "LOCAL", "WND_CLAMPED", "ACTIVE_CLOSE", "ACK_TO_TAP_DUE",
"ACK_FROM_TAP_DUE",
};
/* Listening sockets, used for automatic port forwarding in pasta mode only */
static int tcp_sock_init_ext [NUM_PORTS][IP_VERSIONS];
static int tcp_sock_ns [NUM_PORTS][IP_VERSIONS];
/* Table of guest side forwarding addresses with very low RTT (assumed
* to be local to the host), LRU
*/
static union inany_addr low_rtt_dst[LOW_RTT_TABLE_SIZE];
/**
* tcp_buf_seq_update - Sequences to update with length of frames once sent
* @seq: Pointer to sequence number sent to tap-side, to be updated
* @len: TCP payload length
*/
struct tcp_buf_seq_update {
uint32_t *seq;
uint16_t len;
};
/* Static buffers */
/**
* tcp4_l2_buf_t - Pre-cooked IPv4 packet buffers for tap connections
* @pad: Align TCP header to 32 bytes, for AVX2 checksum calculation only
* @taph: Tap-level headers (partially pre-filled)
* @iph: Pre-filled IP header (except for tot_len and saddr)
* @uh: Headroom for TCP header
* @data: Storage for TCP payload
*/
static struct tcp4_l2_buf_t {
#ifdef __AVX2__
uint8_t pad[26]; /* 0, align th to 32 bytes */
#else
uint8_t pad[2]; /* align iph to 4 bytes 0 */
#endif
struct tap_hdr taph; /* 26 2 */
struct iphdr iph; /* 44 20 */
struct tcphdr th; /* 64 40 */
uint8_t data[MSS4]; /* 84 60 */
/* 65536 65532 */
#ifdef __AVX2__
} __attribute__ ((packed, aligned(32)))
#else
} __attribute__ ((packed, aligned(__alignof__(unsigned int))))
#endif
tcp4_l2_buf[TCP_FRAMES_MEM];
static struct tcp_buf_seq_update tcp4_l2_buf_seq_update[TCP_FRAMES_MEM];
static unsigned int tcp4_l2_buf_used;
/**
* tcp6_l2_buf_t - Pre-cooked IPv6 packet buffers for tap connections
* @pad: Align IPv6 header for checksum calculation to 32B (AVX2) or 4B
* @taph: Tap-level headers (partially pre-filled)
* @ip6h: Pre-filled IP header (except for payload_len and addresses)
* @th: Headroom for TCP header
* @data: Storage for TCP payload
*/
struct tcp6_l2_buf_t {
#ifdef __AVX2__
uint8_t pad[14]; /* 0 align ip6h to 32 bytes */
#else
uint8_t pad[2]; /* align ip6h to 4 bytes 0 */
#endif
struct tap_hdr taph; /* 14 2 */
struct ipv6hdr ip6h; /* 32 20 */
struct tcphdr th; /* 72 60 */
uint8_t data[MSS6]; /* 92 80 */
/* 65536 65532 */
#ifdef __AVX2__
} __attribute__ ((packed, aligned(32)))
#else
} __attribute__ ((packed, aligned(__alignof__(unsigned int))))
#endif
tcp6_l2_buf[TCP_FRAMES_MEM];
static struct tcp_buf_seq_update tcp6_l2_buf_seq_update[TCP_FRAMES_MEM];
static unsigned int tcp6_l2_buf_used;
/* recvmsg()/sendmsg() data for tap */
static char tcp_buf_discard [MAX_WINDOW];
static struct iovec iov_sock [TCP_FRAMES_MEM + 1];
static struct iovec tcp4_l2_iov [TCP_FRAMES_MEM];
static struct iovec tcp6_l2_iov [TCP_FRAMES_MEM];
static struct iovec tcp4_l2_flags_iov [TCP_FRAMES_MEM];
static struct iovec tcp6_l2_flags_iov [TCP_FRAMES_MEM];
static struct mmsghdr tcp_l2_mh [TCP_FRAMES_MEM];
/* sendmsg() to socket */
static struct iovec tcp_iov [UIO_MAXIOV];
/**
* tcp4_l2_flags_buf_t - IPv4 packet buffers for segments without data (flags)
* @pad: Align TCP header to 32 bytes, for AVX2 checksum calculation only
* @taph: Tap-level headers (partially pre-filled)
* @iph: Pre-filled IP header (except for tot_len and saddr)
* @th: Headroom for TCP header
* @opts: Headroom for TCP options
*/
static struct tcp4_l2_flags_buf_t {
#ifdef __AVX2__
uint8_t pad[26]; /* 0, align th to 32 bytes */
#else
uint8_t pad[2]; /* align iph to 4 bytes 0 */
#endif
struct tap_hdr taph; /* 26 2 */
struct iphdr iph; /* 44 20 */
struct tcphdr th; /* 64 40 */
char opts[OPT_MSS_LEN + OPT_WS_LEN + 1];
#ifdef __AVX2__
} __attribute__ ((packed, aligned(32)))
#else
} __attribute__ ((packed, aligned(__alignof__(unsigned int))))
#endif
tcp4_l2_flags_buf[TCP_FRAMES_MEM];
static unsigned int tcp4_l2_flags_buf_used;
/**
* tcp6_l2_flags_buf_t - IPv6 packet buffers for segments without data (flags)
* @pad: Align IPv6 header for checksum calculation to 32B (AVX2) or 4B
* @taph: Tap-level headers (partially pre-filled)
* @ip6h: Pre-filled IP header (except for payload_len and addresses)
* @th: Headroom for TCP header
* @opts: Headroom for TCP options
*/
static struct tcp6_l2_flags_buf_t {
#ifdef __AVX2__
uint8_t pad[14]; /* 0 align ip6h to 32 bytes */
#else
uint8_t pad[2]; /* align ip6h to 4 bytes 0 */
#endif
struct tap_hdr taph; /* 14 2 */
struct ipv6hdr ip6h; /* 32 20 */
struct tcphdr th /* 72 */ __attribute__ ((aligned(4))); /* 60 */
char opts[OPT_MSS_LEN + OPT_WS_LEN + 1];
#ifdef __AVX2__
} __attribute__ ((packed, aligned(32)))
#else
} __attribute__ ((packed, aligned(__alignof__(unsigned int))))
#endif
tcp6_l2_flags_buf[TCP_FRAMES_MEM];
static unsigned int tcp6_l2_flags_buf_used;
/* TCP connections */
union tcp_conn tc[TCP_MAX_CONNS];
#define CONN(idx) (&tc[(idx)].tap)
#define CONN_IDX(conn) ((union tcp_conn *)(conn) - tc)
/** conn_at_idx() - Find a connection by index, if present
* @idx: Index of connection to lookup
*
* Return: pointer to connection, or NULL if @idx is out of bounds
*/
static inline struct tcp_tap_conn *conn_at_idx(int idx)
{
if ((idx < 0) || (idx >= TCP_MAX_CONNS))
return NULL;
ASSERT(!(CONN(idx)->c.spliced));
return CONN(idx);
}
/* Table for lookup from remote address, local port, remote port */
static struct tcp_tap_conn *tc_hash[TCP_HASH_TABLE_SIZE];
/* Pools for pre-opened sockets (in init) */
int init_sock_pool4 [TCP_SOCK_POOL_SIZE];
int init_sock_pool6 [TCP_SOCK_POOL_SIZE];
/**
* tcp_conn_epoll_events() - epoll events mask for given connection state
* @events: Current connection events
* @conn_flags Connection flags
*
* Return: epoll events mask corresponding to implied connection state
*/
static uint32_t tcp_conn_epoll_events(uint8_t events, uint8_t conn_flags)
{
if (!events)
return 0;
if (events & ESTABLISHED) {
if (events & TAP_FIN_SENT)
return EPOLLET;
if (conn_flags & STALLED)
return EPOLLIN | EPOLLOUT | EPOLLRDHUP | EPOLLET;
return EPOLLIN | EPOLLRDHUP;
}
if (events == TAP_SYN_RCVD)
return EPOLLOUT | EPOLLET | EPOLLRDHUP;
return EPOLLRDHUP;
}
static void conn_flag_do(const struct ctx *c, struct tcp_tap_conn *conn,
unsigned long flag);
#define conn_flag(c, conn, flag) \
do { \
trace("TCP: flag at %s:%i", __func__, __LINE__); \
conn_flag_do(c, conn, flag); \
} while (0)
/**
* tcp_epoll_ctl() - Add/modify/delete epoll state from connection events
* @c: Execution context
* @conn: Connection pointer
*
* Return: 0 on success, negative error code on failure (not on deletion)
*/
static int tcp_epoll_ctl(const struct ctx *c, struct tcp_tap_conn *conn)
{
int m = conn->in_epoll ? EPOLL_CTL_MOD : EPOLL_CTL_ADD;
union epoll_ref ref = { .type = EPOLL_TYPE_TCP, .fd = conn->sock,
.tcp.index = CONN_IDX(conn) };
struct epoll_event ev = { .data.u64 = ref.u64 };
if (conn->events == CLOSED) {
if (conn->in_epoll)
epoll_ctl(c->epollfd, EPOLL_CTL_DEL, conn->sock, &ev);
if (conn->timer != -1)
epoll_ctl(c->epollfd, EPOLL_CTL_DEL, conn->timer, &ev);
return 0;
}
ev.events = tcp_conn_epoll_events(conn->events, conn->flags);
if (epoll_ctl(c->epollfd, m, conn->sock, &ev))
return -errno;
conn->in_epoll = true;
if (conn->timer != -1) {
union epoll_ref ref_t = { .type = EPOLL_TYPE_TCP_TIMER,
.fd = conn->sock,
.tcp.index = CONN_IDX(conn) };
struct epoll_event ev_t = { .data.u64 = ref_t.u64,
.events = EPOLLIN | EPOLLET };
if (epoll_ctl(c->epollfd, EPOLL_CTL_MOD, conn->timer, &ev_t))
return -errno;
}
return 0;
}
/**
* tcp_timer_ctl() - Set timerfd based on flags/events, create timerfd if needed
* @c: Execution context
* @conn: Connection pointer
*
* #syscalls timerfd_create timerfd_settime
*/
static void tcp_timer_ctl(const struct ctx *c, struct tcp_tap_conn *conn)
{
struct itimerspec it = { { 0 }, { 0 } };
if (conn->events == CLOSED)
return;
if (conn->timer == -1) {
union epoll_ref ref = { .type = EPOLL_TYPE_TCP_TIMER,
.fd = conn->sock,
.tcp.index = CONN_IDX(conn) };
struct epoll_event ev = { .data.u64 = ref.u64,
.events = EPOLLIN | EPOLLET };
int fd;
fd = timerfd_create(CLOCK_MONOTONIC, 0);
if (fd == -1 || fd > FD_REF_MAX) {
debug("TCP: failed to get timer: %s", strerror(errno));
if (fd > -1)
close(fd);
conn->timer = -1;
return;
}
conn->timer = fd;
if (epoll_ctl(c->epollfd, EPOLL_CTL_ADD, conn->timer, &ev)) {
debug("TCP: failed to add timer: %s", strerror(errno));
close(conn->timer);
conn->timer = -1;
return;
}
}
if (conn->flags & ACK_TO_TAP_DUE) {
it.it_value.tv_nsec = (long)ACK_INTERVAL * 1000 * 1000;
} else if (conn->flags & ACK_FROM_TAP_DUE) {
if (!(conn->events & ESTABLISHED))
it.it_value.tv_sec = SYN_TIMEOUT;
else
it.it_value.tv_sec = ACK_TIMEOUT;
} else if (CONN_HAS(conn, SOCK_FIN_SENT | TAP_FIN_ACKED)) {
it.it_value.tv_sec = FIN_TIMEOUT;
} else {
it.it_value.tv_sec = ACT_TIMEOUT;
}
debug("TCP: index %li, timer expires in %lu.%03lus", CONN_IDX(conn),
it.it_value.tv_sec, it.it_value.tv_nsec / 1000 / 1000);
timerfd_settime(conn->timer, 0, &it, NULL);
}
/**
* conn_flag_do() - Set/unset given flag, log, update epoll on STALLED flag
* @c: Execution context
* @conn: Connection pointer
* @flag: Flag to set, or ~flag to unset
*/
static void conn_flag_do(const struct ctx *c, struct tcp_tap_conn *conn,
unsigned long flag)
{
if (flag & (flag - 1)) {
int flag_index = fls(~flag);
if (!(conn->flags & ~flag))
return;
conn->flags &= flag;
if (flag_index >= 0) {
debug("TCP: index %li: %s dropped", CONN_IDX(conn),
tcp_flag_str[flag_index]);
}
} else {
int flag_index = fls(flag);
if (conn->flags & flag) {
/* Special case: setting ACK_FROM_TAP_DUE on a
* connection where it's already set is used to
* re-schedule the existing timer.
* TODO: define clearer semantics for timer-related
* flags and factor this into the logic below.
*/
if (flag == ACK_FROM_TAP_DUE)
tcp_timer_ctl(c, conn);
return;
}
conn->flags |= flag;
if (flag_index >= 0) {
debug("TCP: index %li: %s", CONN_IDX(conn),
tcp_flag_str[flag_index]);
}
}
if (flag == STALLED || flag == ~STALLED)
tcp_epoll_ctl(c, conn);
if (flag == ACK_FROM_TAP_DUE || flag == ACK_TO_TAP_DUE ||
(flag == ~ACK_FROM_TAP_DUE && (conn->flags & ACK_TO_TAP_DUE)) ||
(flag == ~ACK_TO_TAP_DUE && (conn->flags & ACK_FROM_TAP_DUE)))
tcp_timer_ctl(c, conn);
}
/**
* conn_event_do() - Set and log connection events, update epoll state
* @c: Execution context
* @conn: Connection pointer
* @event: Connection event
*/
static void conn_event_do(const struct ctx *c, struct tcp_tap_conn *conn,
unsigned long event)
{
int prev, new, num = fls(event);
if (conn->events & event)
return;
prev = fls(conn->events);
if (conn->flags & ACTIVE_CLOSE)
prev += 5;
if ((conn->events & ESTABLISHED) && (conn->events != ESTABLISHED))
prev++; /* i.e. SOCK_FIN_RCVD, not TAP_SYN_ACK_SENT */
if (event == CLOSED || (event & CONN_STATE_BITS))
conn->events = event;
else
conn->events |= event;
new = fls(conn->events);
if ((conn->events & ESTABLISHED) && (conn->events != ESTABLISHED)) {
num++;
new++;
}
if (conn->flags & ACTIVE_CLOSE)
new += 5;
if (prev != new) {
debug("TCP: index %li, %s: %s -> %s", CONN_IDX(conn),
num == -1 ? "CLOSED" : tcp_event_str[num],
prev == -1 ? "CLOSED" : tcp_state_str[prev],
(new == -1 || num == -1) ? "CLOSED" : tcp_state_str[new]);
} else {
debug("TCP: index %li, %s", CONN_IDX(conn),
num == -1 ? "CLOSED" : tcp_event_str[num]);
}
if ((event == TAP_FIN_RCVD) && !(conn->events & SOCK_FIN_RCVD))
conn_flag(c, conn, ACTIVE_CLOSE);
else
tcp_epoll_ctl(c, conn);
if (CONN_HAS(conn, SOCK_FIN_SENT | TAP_FIN_ACKED))
tcp_timer_ctl(c, conn);
}
#define conn_event(c, conn, event) \
do { \
trace("TCP: event at %s:%i", __func__, __LINE__); \
conn_event_do(c, conn, event); \
} while (0)
/**
* tcp_rtt_dst_low() - Check if low RTT was seen for connection endpoint
* @conn: Connection pointer
*
* Return: 1 if destination is in low RTT table, 0 otherwise
*/
static int tcp_rtt_dst_low(const struct tcp_tap_conn *conn)
{
int i;
for (i = 0; i < LOW_RTT_TABLE_SIZE; i++)
if (inany_equals(&conn->faddr, low_rtt_dst + i))
return 1;
return 0;
}
/**
* tcp_rtt_dst_check() - Check tcpi_min_rtt, insert endpoint in table if low
* @conn: Connection pointer
* @tinfo: Pointer to struct tcp_info for socket
*/
static void tcp_rtt_dst_check(const struct tcp_tap_conn *conn,
const struct tcp_info *tinfo)
{
#ifdef HAS_MIN_RTT
int i, hole = -1;
if (!tinfo->tcpi_min_rtt ||
(int)tinfo->tcpi_min_rtt > LOW_RTT_THRESHOLD)
return;
for (i = 0; i < LOW_RTT_TABLE_SIZE; i++) {
if (inany_equals(&conn->faddr, low_rtt_dst + i))
return;
if (hole == -1 && IN6_IS_ADDR_UNSPECIFIED(low_rtt_dst + i))
hole = i;
}
/* Keep gcc 12 happy: this won't actually happen because the table is
* guaranteed to have a hole, see the second memcpy() below.
*/
if (hole == -1)
return;
low_rtt_dst[hole++] = conn->faddr;
if (hole == LOW_RTT_TABLE_SIZE)
hole = 0;
inany_from_af(low_rtt_dst + hole, AF_INET6, &in6addr_any);
#else
(void)conn;
(void)tinfo;
#endif /* HAS_MIN_RTT */
}
/**
* tcp_get_sndbuf() - Get, scale SO_SNDBUF between thresholds (1 to 0.5 usage)
* @conn: Connection pointer
*/
static void tcp_get_sndbuf(struct tcp_tap_conn *conn)
{
int s = conn->sock, sndbuf;
socklen_t sl;
uint64_t v;
sl = sizeof(sndbuf);
if (getsockopt(s, SOL_SOCKET, SO_SNDBUF, &sndbuf, &sl)) {
SNDBUF_SET(conn, WINDOW_DEFAULT);
return;
}
v = sndbuf;
if (v >= SNDBUF_BIG)
v /= 2;
else if (v > SNDBUF_SMALL)
v -= v * (v - SNDBUF_SMALL) / (SNDBUF_BIG - SNDBUF_SMALL) / 2;
SNDBUF_SET(conn, MIN(INT_MAX, v));
}
/**
* tcp_sock_set_bufsize() - Set SO_RCVBUF and SO_SNDBUF to maximum values
* @s: Socket, can be -1 to avoid check in the caller
*/
void tcp_sock_set_bufsize(const struct ctx *c, int s)
{
int v = INT_MAX / 2; /* Kernel clamps and rounds, no need to check */
if (s == -1)
return;
if (!c->low_rmem && setsockopt(s, SOL_SOCKET, SO_RCVBUF, &v, sizeof(v)))
trace("TCP: failed to set SO_RCVBUF to %i", v);
if (!c->low_wmem && setsockopt(s, SOL_SOCKET, SO_SNDBUF, &v, sizeof(v)))
trace("TCP: failed to set SO_SNDBUF to %i", v);
}
/**
* tcp_update_check_ip4() - Update IPv4 with variable parts from stored one
* @buf: L2 packet buffer with final IPv4 header
*/
static void tcp_update_check_ip4(struct tcp4_l2_buf_t *buf)
{
uint32_t sum = L2_BUF_IP4_PSUM(IPPROTO_TCP);
sum += buf->iph.tot_len;
sum += (buf->iph.saddr >> 16) & 0xffff;
sum += buf->iph.saddr & 0xffff;
sum += (buf->iph.daddr >> 16) & 0xffff;
sum += buf->iph.daddr & 0xffff;
buf->iph.check = (uint16_t)~csum_fold(sum);
}
/**
* tcp_update_check_tcp4() - Update TCP checksum from stored one
* @buf: L2 packet buffer with final IPv4 header
*/
static void tcp_update_check_tcp4(struct tcp4_l2_buf_t *buf)
{
uint16_t tlen = ntohs(buf->iph.tot_len) - 20;
uint32_t sum = htons(IPPROTO_TCP);
sum += (buf->iph.saddr >> 16) & 0xffff;
sum += buf->iph.saddr & 0xffff;
sum += (buf->iph.daddr >> 16) & 0xffff;
sum += buf->iph.daddr & 0xffff;
sum += htons(ntohs(buf->iph.tot_len) - 20);
buf->th.check = 0;
buf->th.check = csum(&buf->th, tlen, sum);
}
/**
* tcp_update_check_tcp6() - Calculate TCP checksum for IPv6
* @buf: L2 packet buffer with final IPv6 header
*/
static void tcp_update_check_tcp6(struct tcp6_l2_buf_t *buf)
{
int len = ntohs(buf->ip6h.payload_len) + sizeof(struct ipv6hdr);
buf->ip6h.hop_limit = IPPROTO_TCP;
buf->ip6h.version = 0;
buf->ip6h.nexthdr = 0;
buf->th.check = 0;
buf->th.check = csum(&buf->ip6h, len, 0);
buf->ip6h.hop_limit = 255;
buf->ip6h.version = 6;
buf->ip6h.nexthdr = IPPROTO_TCP;
}
/**
* tcp_update_l2_buf() - Update L2 buffers with Ethernet and IPv4 addresses
* @eth_d: Ethernet destination address, NULL if unchanged
* @eth_s: Ethernet source address, NULL if unchanged
*/
void tcp_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s)
{
int i;
for (i = 0; i < TCP_FRAMES_MEM; i++) {
struct tcp4_l2_flags_buf_t *b4f = &tcp4_l2_flags_buf[i];
struct tcp6_l2_flags_buf_t *b6f = &tcp6_l2_flags_buf[i];
struct tcp4_l2_buf_t *b4 = &tcp4_l2_buf[i];
struct tcp6_l2_buf_t *b6 = &tcp6_l2_buf[i];
tap_update_mac(&b4->taph, eth_d, eth_s);
tap_update_mac(&b6->taph, eth_d, eth_s);
tap_update_mac(&b4f->taph, eth_d, eth_s);
tap_update_mac(&b6f->taph, eth_d, eth_s);
}
}
/**
* tcp_sock4_iov_init() - Initialise scatter-gather L2 buffers for IPv4 sockets
* @c: Execution context
*/
static void tcp_sock4_iov_init(const struct ctx *c)
{
struct iphdr iph = L2_BUF_IP4_INIT(IPPROTO_TCP);
struct iovec *iov;
int i;
for (i = 0; i < ARRAY_SIZE(tcp4_l2_buf); i++) {
tcp4_l2_buf[i] = (struct tcp4_l2_buf_t) {
.taph = TAP_HDR_INIT(ETH_P_IP),
.iph = iph,
.th = { .doff = sizeof(struct tcphdr) / 4, .ack = 1 }
};
}
for (i = 0; i < ARRAY_SIZE(tcp4_l2_flags_buf); i++) {
tcp4_l2_flags_buf[i] = (struct tcp4_l2_flags_buf_t) {
.taph = TAP_HDR_INIT(ETH_P_IP),
.iph = L2_BUF_IP4_INIT(IPPROTO_TCP)
};
}
for (i = 0, iov = tcp4_l2_iov; i < TCP_FRAMES_MEM; i++, iov++)
iov->iov_base = tap_iov_base(c, &tcp4_l2_buf[i].taph);
for (i = 0, iov = tcp4_l2_flags_iov; i < TCP_FRAMES_MEM; i++, iov++)
iov->iov_base = tap_iov_base(c, &tcp4_l2_flags_buf[i].taph);
}
/**
* tcp_sock6_iov_init() - Initialise scatter-gather L2 buffers for IPv6 sockets
* @c: Execution context
*/
static void tcp_sock6_iov_init(const struct ctx *c)
{
struct iovec *iov;
int i;
for (i = 0; i < ARRAY_SIZE(tcp6_l2_buf); i++) {
tcp6_l2_buf[i] = (struct tcp6_l2_buf_t) {
.taph = TAP_HDR_INIT(ETH_P_IPV6),
.ip6h = L2_BUF_IP6_INIT(IPPROTO_TCP),
.th = { .doff = sizeof(struct tcphdr) / 4, .ack = 1 }
};
}
for (i = 0; i < ARRAY_SIZE(tcp6_l2_flags_buf); i++) {
tcp6_l2_flags_buf[i] = (struct tcp6_l2_flags_buf_t) {
.taph = TAP_HDR_INIT(ETH_P_IPV6),
.ip6h = L2_BUF_IP6_INIT(IPPROTO_TCP)
};
}
for (i = 0, iov = tcp6_l2_iov; i < TCP_FRAMES_MEM; i++, iov++)
iov->iov_base = tap_iov_base(c, &tcp6_l2_buf[i].taph);
for (i = 0, iov = tcp6_l2_flags_iov; i < TCP_FRAMES_MEM; i++, iov++)
iov->iov_base = tap_iov_base(c, &tcp6_l2_flags_buf[i].taph);
}
/**
* tcp_opt_get() - Get option, and value if any, from TCP header
* @opts: Pointer to start of TCP options in header
* @len: Length of buffer, excluding TCP header -- NOT checked here!
* @type_find: Option type to look for
* @optlen_set: Optional, filled with option length if passed
* @value_set: Optional, set to start of option value if passed
*
* Return: option value, meaningful for up to 4 bytes, -1 if not found
*/
static int tcp_opt_get(const char *opts, size_t len, uint8_t type_find,
uint8_t *optlen_set, const char **value_set)
{
uint8_t type, optlen;
if (!opts || !len)
return -1;
for (; len >= 2; opts += optlen, len -= optlen) {
switch (*opts) {
case OPT_EOL:
return -1;
case OPT_NOP:
optlen = 1;
break;
default:
type = *(opts++);
if (*(uint8_t *)opts < 2 || *(uint8_t *)opts > len)
return -1;
optlen = *(opts++) - 2;
len -= 2;
if (type != type_find)
break;
if (optlen_set)
*optlen_set = optlen;
if (value_set)
*value_set = opts;
switch (optlen) {
case 0:
return 0;
case 1:
return *opts;
case 2:
return ntohs(*(uint16_t *)opts);
default:
return ntohl(*(uint32_t *)opts);
}
}
}
return -1;
}
/**
* tcp_hash_match() - Check if a connection entry matches address and ports
* @conn: Connection entry to match against
* @faddr: Guest side forwarding address
* @eport: Guest side endpoint port
* @fport: Guest side forwarding port
*
* Return: 1 on match, 0 otherwise
*/
static int tcp_hash_match(const struct tcp_tap_conn *conn,
const union inany_addr *faddr,
in_port_t eport, in_port_t fport)
{
if (conn->events != CLOSED && inany_equals(&conn->faddr, faddr) &&
conn->eport == eport && conn->fport == fport)
return 1;
return 0;
}
/**
* tcp_hash() - Calculate hash value for connection given address and ports
* @c: Execution context
* @faddr: Guest side forwarding address
* @eport: Guest side endpoint port
* @fport: Guest side forwarding port
*
* Return: hash value, already modulo size of the hash table
*/
static unsigned int tcp_hash(const struct ctx *c, const union inany_addr *faddr,
in_port_t eport, in_port_t fport)
{
struct siphash_state state = SIPHASH_INIT(c->tcp.hash_secret);
uint64_t hash;
inany_siphash_feed(&state, faddr);
hash = siphash_final(&state, 20, (uint64_t)eport << 16 | fport);
return (unsigned int)(hash % TCP_HASH_TABLE_SIZE);
}
/**
* tcp_conn_hash() - Calculate hash bucket of an existing connection
* @c: Execution context
* @conn: Connection
*
* Return: hash value, already modulo size of the hash table
*/
static unsigned int tcp_conn_hash(const struct ctx *c,
const struct tcp_tap_conn *conn)
{
return tcp_hash(c, &conn->faddr, conn->eport, conn->fport);
}
/**
* tcp_hash_insert() - Insert connection into hash table, chain link
* @c: Execution context
* @conn: Connection pointer
*/
static void tcp_hash_insert(const struct ctx *c, struct tcp_tap_conn *conn)
{
int b;
b = tcp_hash(c, &conn->faddr, conn->eport, conn->fport);
conn->next_index = tc_hash[b] ? CONN_IDX(tc_hash[b]) : -1;
tc_hash[b] = conn;
debug("TCP: hash table insert: index %li, sock %i, bucket: %i, next: "
"%p", CONN_IDX(conn), conn->sock, b, conn_at_idx(conn->next_index));
}
/**
* tcp_hash_remove() - Drop connection from hash table, chain unlink
* @c: Execution context
* @conn: Connection pointer
*/
static void tcp_hash_remove(const struct ctx *c,
const struct tcp_tap_conn *conn)
{
struct tcp_tap_conn *entry, *prev = NULL;
int b = tcp_conn_hash(c, conn);
for (entry = tc_hash[b]; entry;
prev = entry, entry = conn_at_idx(entry->next_index)) {
if (entry == conn) {
if (prev)
prev->next_index = conn->next_index;
else
tc_hash[b] = conn_at_idx(conn->next_index);
break;
}
}
debug("TCP: hash table remove: index %li, sock %i, bucket: %i, new: %p",
CONN_IDX(conn), conn->sock, b,
prev ? conn_at_idx(prev->next_index) : tc_hash[b]);
}
/**
* tcp_tap_conn_update() - Update tcp_tap_conn when being moved in the table
* @c: Execution context
* @old: Old location of tcp_tap_conn
* @new: New location of tcp_tap_conn
*/
static void tcp_tap_conn_update(const struct ctx *c, struct tcp_tap_conn *old,
struct tcp_tap_conn *new)
{
struct tcp_tap_conn *entry, *prev = NULL;
int b = tcp_conn_hash(c, old);
for (entry = tc_hash[b]; entry;
prev = entry, entry = conn_at_idx(entry->next_index)) {
if (entry == old) {
if (prev)
prev->next_index = CONN_IDX(new);
else
tc_hash[b] = new;
break;
}
}
debug("TCP: hash table update: old index %li, new index %li, sock %i, "
"bucket: %i, old: %p, new: %p",
CONN_IDX(old), CONN_IDX(new), new->sock, b, old, new);
tcp_epoll_ctl(c, new);
}
/**
* tcp_hash_lookup() - Look up connection given remote address and ports
* @c: Execution context
* @af: Address family, AF_INET or AF_INET6
* @faddr: Guest side forwarding address (guest remote address)
* @eport: Guest side endpoint port (guest local port)
* @fport: Guest side forwarding port (guest remote port)
*
* Return: connection pointer, if found, -ENOENT otherwise
*/
static struct tcp_tap_conn *tcp_hash_lookup(const struct ctx *c,
int af, const void *faddr,
in_port_t eport, in_port_t fport)
{
union inany_addr aany;
struct tcp_tap_conn *conn;
int b;
inany_from_af(&aany, af, faddr);
b = tcp_hash(c, &aany, eport, fport);
for (conn = tc_hash[b]; conn; conn = conn_at_idx(conn->next_index)) {
if (tcp_hash_match(conn, &aany, eport, fport))
return conn;
}
return NULL;
}
/**
* tcp_table_compact() - Perform compaction on connection table
* @c: Execution context
* @hole: Pointer to recently closed connection
*/
void tcp_table_compact(struct ctx *c, union tcp_conn *hole)
{
union tcp_conn *from;
if (CONN_IDX(hole) == --c->tcp.conn_count) {
debug("TCP: table compaction: maximum index was %li (%p)",
CONN_IDX(hole), hole);
memset(hole, 0, sizeof(*hole));
return;
}
from = tc + c->tcp.conn_count;
memcpy(hole, from, sizeof(*hole));
if (from->c.spliced)
tcp_splice_conn_update(c, &hole->splice);
else
tcp_tap_conn_update(c, &from->tap, &hole->tap);
debug("TCP: table compaction (spliced=%d): old index %li, new index %li, "
"from: %p, to: %p",
from->c.spliced, CONN_IDX(from), CONN_IDX(hole), from, hole);
memset(from, 0, sizeof(*from));
}
/**
* tcp_conn_destroy() - Close sockets, trigger hash table removal and compaction
* @c: Execution context
* @conn_union: Connection pointer (container union)
*/
static void tcp_conn_destroy(struct ctx *c, union tcp_conn *conn_union)
{
const struct tcp_tap_conn *conn = &conn_union->tap;
close(conn->sock);
if (conn->timer != -1)
close(conn->timer);
tcp_hash_remove(c, conn);
tcp_table_compact(c, conn_union);
}
static void tcp_rst_do(struct ctx *c, struct tcp_tap_conn *conn);
#define tcp_rst(c, conn) \
do { \
debug("TCP: index %li, reset at %s:%i", CONN_IDX(conn), \
__func__, __LINE__); \
tcp_rst_do(c, conn); \
} while (0)
/**
* tcp_l2_flags_buf_flush() - Send out buffers for segments with no data (flags)
* @c: Execution context
*/
static void tcp_l2_flags_buf_flush(const struct ctx *c)
{
tap_send_frames(c, tcp6_l2_flags_iov, tcp6_l2_flags_buf_used);
tcp6_l2_flags_buf_used = 0;
tap_send_frames(c, tcp4_l2_flags_iov, tcp4_l2_flags_buf_used);
tcp4_l2_flags_buf_used = 0;
}
/**
* tcp_l2_data_buf_flush() - Send out buffers for segments with data
* @c: Execution context
*/
static void tcp_l2_data_buf_flush(const struct ctx *c)
{
unsigned i;
size_t m;
m = tap_send_frames(c, tcp6_l2_iov, tcp6_l2_buf_used);
for (i = 0; i < m; i++)
*tcp6_l2_buf_seq_update[i].seq += tcp6_l2_buf_seq_update[i].len;
tcp6_l2_buf_used = 0;
m = tap_send_frames(c, tcp4_l2_iov, tcp4_l2_buf_used);
for (i = 0; i < m; i++)
*tcp4_l2_buf_seq_update[i].seq += tcp4_l2_buf_seq_update[i].len;
tcp4_l2_buf_used = 0;
}
/**
* tcp_defer_handler() - Handler for TCP deferred tasks
* @c: Execution context
*/
void tcp_defer_handler(struct ctx *c)
{
union tcp_conn *conn;
tcp_l2_flags_buf_flush(c);
tcp_l2_data_buf_flush(c);
for (conn = tc + c->tcp.conn_count - 1; conn >= tc; conn--) {
if (conn->c.spliced) {
if (conn->splice.flags & CLOSING)
tcp_splice_destroy(c, conn);
} else {
if (conn->tap.events == CLOSED)
tcp_conn_destroy(c, conn);
}
}
}
/**
* tcp_l2_buf_fill_headers() - Fill 802.3, IP, TCP headers in pre-cooked buffers
* @c: Execution context
* @conn: Connection pointer
* @p: Pointer to any type of TCP pre-cooked buffer
* @plen: Payload length (including TCP header options)
* @check: Checksum, if already known
* @seq: Sequence number for this segment
*
* Return: frame length including L2 headers, host order
*/
static size_t tcp_l2_buf_fill_headers(const struct ctx *c,
const struct tcp_tap_conn *conn,
void *p, size_t plen,
const uint16_t *check, uint32_t seq)
{
const struct in_addr *a4 = inany_v4(&conn->faddr);
size_t ip_len, tlen;
#define SET_TCP_HEADER_COMMON_V4_V6(b, conn, seq) \
do { \
b->th.source = htons(conn->fport); \
b->th.dest = htons(conn->eport); \
b->th.seq = htonl(seq); \
b->th.ack_seq = htonl(conn->seq_ack_to_tap); \
if (conn->events & ESTABLISHED) { \
b->th.window = htons(conn->wnd_to_tap); \
} else { \
unsigned wnd = conn->wnd_to_tap << conn->ws_to_tap; \
\
b->th.window = htons(MIN(wnd, USHRT_MAX)); \
} \
} while (0)
if (a4) {
struct tcp4_l2_buf_t *b = (struct tcp4_l2_buf_t *)p;
ip_len = plen + sizeof(struct iphdr) + sizeof(struct tcphdr);
b->iph.tot_len = htons(ip_len);
b->iph.saddr = a4->s_addr;
b->iph.daddr = c->ip4.addr_seen.s_addr;
if (check)
b->iph.check = *check;
else
tcp_update_check_ip4(b);
SET_TCP_HEADER_COMMON_V4_V6(b, conn, seq);
tcp_update_check_tcp4(b);
tlen = tap_iov_len(c, &b->taph, ip_len);
} else {
struct tcp6_l2_buf_t *b = (struct tcp6_l2_buf_t *)p;
ip_len = plen + sizeof(struct ipv6hdr) + sizeof(struct tcphdr);
b->ip6h.payload_len = htons(plen + sizeof(struct tcphdr));
b->ip6h.saddr = conn->faddr.a6;
if (IN6_IS_ADDR_LINKLOCAL(&b->ip6h.saddr))
b->ip6h.daddr = c->ip6.addr_ll_seen;
else
b->ip6h.daddr = c->ip6.addr_seen;
memset(b->ip6h.flow_lbl, 0, 3);
SET_TCP_HEADER_COMMON_V4_V6(b, conn, seq);
tcp_update_check_tcp6(b);
b->ip6h.flow_lbl[0] = (conn->sock >> 16) & 0xf;
b->ip6h.flow_lbl[1] = (conn->sock >> 8) & 0xff;
b->ip6h.flow_lbl[2] = (conn->sock >> 0) & 0xff;
tlen = tap_iov_len(c, &b->taph, ip_len);
}
#undef SET_TCP_HEADER_COMMON_V4_V6
return tlen;
}
/**
* tcp_update_seqack_wnd() - Update ACK sequence and window to guest/tap
* @c: Execution context
* @conn: Connection pointer
* @force_seq: Force ACK sequence to latest segment, instead of checking socket
* @tinfo: tcp_info from kernel, can be NULL if not pre-fetched
*
* Return: 1 if sequence or window were updated, 0 otherwise
*/
static int tcp_update_seqack_wnd(const struct ctx *c, struct tcp_tap_conn *conn,
int force_seq, struct tcp_info *tinfo)
{
uint32_t prev_wnd_to_tap = conn->wnd_to_tap << conn->ws_to_tap;
uint32_t prev_ack_to_tap = conn->seq_ack_to_tap;
/* cppcheck-suppress [ctunullpointer, unmatchedSuppression] */
socklen_t sl = sizeof(*tinfo);
struct tcp_info tinfo_new;
uint32_t new_wnd_to_tap = prev_wnd_to_tap;
int s = conn->sock;
#ifndef HAS_BYTES_ACKED
(void)force_seq;
conn->seq_ack_to_tap = conn->seq_from_tap;
if (SEQ_LT(conn->seq_ack_to_tap, prev_ack_to_tap))
conn->seq_ack_to_tap = prev_ack_to_tap;
#else
if ((unsigned)SNDBUF_GET(conn) < SNDBUF_SMALL || tcp_rtt_dst_low(conn)
|| CONN_IS_CLOSING(conn) || (conn->flags & LOCAL) || force_seq) {
conn->seq_ack_to_tap = conn->seq_from_tap;
} else if (conn->seq_ack_to_tap != conn->seq_from_tap) {
if (!tinfo) {
tinfo = &tinfo_new;
if (getsockopt(s, SOL_TCP, TCP_INFO, tinfo, &sl))
return 0;
}
conn->seq_ack_to_tap = tinfo->tcpi_bytes_acked +
conn->seq_init_from_tap;
if (SEQ_LT(conn->seq_ack_to_tap, prev_ack_to_tap))
conn->seq_ack_to_tap = prev_ack_to_tap;
}
#endif /* !HAS_BYTES_ACKED */
if (!KERNEL_REPORTS_SND_WND(c)) {
tcp_get_sndbuf(conn);
new_wnd_to_tap = MIN(SNDBUF_GET(conn), MAX_WINDOW);
conn->wnd_to_tap = MIN(new_wnd_to_tap >> conn->ws_to_tap,
USHRT_MAX);
goto out;
}
if (!tinfo) {
if (prev_wnd_to_tap > WINDOW_DEFAULT) {
goto out;
}
tinfo = &tinfo_new;
if (getsockopt(s, SOL_TCP, TCP_INFO, tinfo, &sl)) {
goto out;
}
}
#ifdef HAS_SND_WND
if ((conn->flags & LOCAL) || tcp_rtt_dst_low(conn)) {
new_wnd_to_tap = tinfo->tcpi_snd_wnd;
} else {
tcp_get_sndbuf(conn);
new_wnd_to_tap = MIN((int)tinfo->tcpi_snd_wnd,
SNDBUF_GET(conn));
}
#endif
new_wnd_to_tap = MIN(new_wnd_to_tap, MAX_WINDOW);
if (!(conn->events & ESTABLISHED))
new_wnd_to_tap = MAX(new_wnd_to_tap, WINDOW_DEFAULT);
conn->wnd_to_tap = MIN(new_wnd_to_tap >> conn->ws_to_tap, USHRT_MAX);
/* Certain cppcheck versions, e.g. 2.12.0 have a bug where they think
* the MIN() above restricts conn->wnd_to_tap to be zero. That's
* clearly incorrect, but until the bug is fixed, work around it.
* https://bugzilla.redhat.com/show_bug.cgi?id=2240705
* https://sourceforge.net/p/cppcheck/discussion/general/thread/f5b1a00646/
*/
/* cppcheck-suppress [knownConditionTrueFalse, unmatchedSuppression] */
if (!conn->wnd_to_tap)
conn_flag(c, conn, ACK_TO_TAP_DUE);
out:
return new_wnd_to_tap != prev_wnd_to_tap ||
conn->seq_ack_to_tap != prev_ack_to_tap;
}
/**
* tcp_update_seqack_from_tap() - ACK number from tap and related flags/counters
* @c: Execution context
* @conn: Connection pointer
* @seq Current ACK sequence, host order
*/
static void tcp_update_seqack_from_tap(const struct ctx *c,
struct tcp_tap_conn *conn, uint32_t seq)
{
if (seq == conn->seq_to_tap)
conn_flag(c, conn, ~ACK_FROM_TAP_DUE);
if (SEQ_GT(seq, conn->seq_ack_from_tap)) {
/* Forward progress, but more data to acknowledge: reschedule */
if (SEQ_LT(seq, conn->seq_to_tap))
conn_flag(c, conn, ACK_FROM_TAP_DUE);
conn->retrans = 0;
conn->seq_ack_from_tap = seq;
}
}
/**
* tcp_send_flag() - Send segment with flags to tap (no payload)
* @c: Execution context
* @conn: Connection pointer
* @flags: TCP flags: if not set, send segment only if ACK is due
*
* Return: negative error code on connection reset, 0 otherwise
*/
static int tcp_send_flag(struct ctx *c, struct tcp_tap_conn *conn, int flags)
{
uint32_t prev_ack_to_tap = conn->seq_ack_to_tap;
uint32_t prev_wnd_to_tap = conn->wnd_to_tap;
struct tcp4_l2_flags_buf_t *b4 = NULL;
struct tcp6_l2_flags_buf_t *b6 = NULL;
struct tcp_info tinfo = { 0 };
socklen_t sl = sizeof(tinfo);
int s = conn->sock;
size_t optlen = 0;
struct iovec *iov;
struct tcphdr *th;
char *data;
void *p;
if (SEQ_GE(conn->seq_ack_to_tap, conn->seq_from_tap) &&
!flags && conn->wnd_to_tap)
return 0;
if (getsockopt(s, SOL_TCP, TCP_INFO, &tinfo, &sl)) {
conn_event(c, conn, CLOSED);
return -ECONNRESET;
}
#ifdef HAS_SND_WND
if (!c->tcp.kernel_snd_wnd && tinfo.tcpi_snd_wnd)
c->tcp.kernel_snd_wnd = 1;
#endif
if (!(conn->flags & LOCAL))
tcp_rtt_dst_check(conn, &tinfo);
if (!tcp_update_seqack_wnd(c, conn, flags, &tinfo) && !flags)
return 0;
if (CONN_V4(conn)) {
iov = tcp4_l2_flags_iov + tcp4_l2_flags_buf_used;
p = b4 = tcp4_l2_flags_buf + tcp4_l2_flags_buf_used++;
th = &b4->th;
/* gcc 11.2 would complain on data = (char *)(th + 1); */
data = b4->opts;
} else {
iov = tcp6_l2_flags_iov + tcp6_l2_flags_buf_used;
p = b6 = tcp6_l2_flags_buf + tcp6_l2_flags_buf_used++;
th = &b6->th;
data = b6->opts;
}
if (flags & SYN) {
int mss;
/* Options: MSS, NOP and window scale (8 bytes) */
optlen = OPT_MSS_LEN + 1 + OPT_WS_LEN;
*data++ = OPT_MSS;
*data++ = OPT_MSS_LEN;
if (c->mtu == -1) {
mss = tinfo.tcpi_snd_mss;
} else {
mss = c->mtu - sizeof(struct tcphdr);
if (CONN_V4(conn))
mss -= sizeof(struct iphdr);
else
mss -= sizeof(struct ipv6hdr);
if (c->low_wmem &&
!(conn->flags & LOCAL) && !tcp_rtt_dst_low(conn))
mss = MIN(mss, PAGE_SIZE);
else if (mss > PAGE_SIZE)
mss = ROUND_DOWN(mss, PAGE_SIZE);
}
*(uint16_t *)data = htons(MIN(USHRT_MAX, mss));
data += OPT_MSS_LEN - 2;
th->doff += OPT_MSS_LEN / 4;
conn->ws_to_tap = MIN(MAX_WS, tinfo.tcpi_snd_wscale);
*data++ = OPT_NOP;
*data++ = OPT_WS;
*data++ = OPT_WS_LEN;
*data++ = conn->ws_to_tap;
th->ack = !!(flags & ACK);
} else {
th->ack = !!(flags & (ACK | DUP_ACK)) ||
conn->seq_ack_to_tap != prev_ack_to_tap ||
!prev_wnd_to_tap;
}
th->doff = (sizeof(*th) + optlen) / 4;
th->rst = !!(flags & RST);
th->syn = !!(flags & SYN);
th->fin = !!(flags & FIN);
iov->iov_len = tcp_l2_buf_fill_headers(c, conn, p, optlen,
NULL, conn->seq_to_tap);
if (th->ack) {
if (SEQ_GE(conn->seq_ack_to_tap, conn->seq_from_tap))
conn_flag(c, conn, ~ACK_TO_TAP_DUE);
else
conn_flag(c, conn, ACK_TO_TAP_DUE);
}
if (th->fin)
conn_flag(c, conn, ACK_FROM_TAP_DUE);
/* RFC 793, 3.1: "[...] and the first data octet is ISN+1." */
if (th->fin || th->syn)
conn->seq_to_tap++;
if (CONN_V4(conn)) {
if (flags & DUP_ACK) {
memcpy(b4 + 1, b4, sizeof(*b4));
(iov + 1)->iov_len = iov->iov_len;
tcp4_l2_flags_buf_used++;
}
if (tcp4_l2_flags_buf_used > ARRAY_SIZE(tcp4_l2_flags_buf) - 2)
tcp_l2_flags_buf_flush(c);
} else {
if (flags & DUP_ACK) {
memcpy(b6 + 1, b6, sizeof(*b6));
(iov + 1)->iov_len = iov->iov_len;
tcp6_l2_flags_buf_used++;
}
if (tcp6_l2_flags_buf_used > ARRAY_SIZE(tcp6_l2_flags_buf) - 2)
tcp_l2_flags_buf_flush(c);
}
return 0;
}
/**
* tcp_rst_do() - Reset a tap connection: send RST segment to tap, close socket
* @c: Execution context
* @conn: Connection pointer
*/
static void tcp_rst_do(struct ctx *c, struct tcp_tap_conn *conn)
{
if (conn->events == CLOSED)
return;
if (!tcp_send_flag(c, conn, RST))
conn_event(c, conn, CLOSED);
}
/**
* tcp_get_tap_ws() - Get Window Scaling option for connection from tap/guest
* @conn: Connection pointer
* @opts: Pointer to start of TCP options
* @optlen: Bytes in options: caller MUST ensure available length
*/
static void tcp_get_tap_ws(struct tcp_tap_conn *conn,
const char *opts, size_t optlen)
{
int ws = tcp_opt_get(opts, optlen, OPT_WS, NULL, NULL);
if (ws >= 0 && ws <= TCP_WS_MAX)
conn->ws_from_tap = ws;
else
conn->ws_from_tap = 0;
}
/**
* tcp_clamp_window() - Set new window for connection, clamp on socket
* @c: Execution context
* @conn: Connection pointer
* @window: Window value, host order, unscaled
*/
static void tcp_clamp_window(const struct ctx *c, struct tcp_tap_conn *conn,
unsigned wnd)
{
uint32_t prev_scaled = conn->wnd_from_tap << conn->ws_from_tap;
int s = conn->sock;
wnd <<= conn->ws_from_tap;
wnd = MIN(MAX_WINDOW, wnd);
/* TODO: With (at least) Linux kernel versions 6.1 to 6.5, if we end up
* with a zero-sized window on a TCP socket, dropping data (once
* acknowledged by the guest) with recv() and MSG_TRUNC doesn't appear
* to be enough to make the kernel advertise a non-zero window to the
* sender. Forcing a TCP_WINDOW_CLAMP setting, even with the existing
* value, fixes this.
*
* The STALLED flag on a connection is a sufficient indication that we
* might have a zero-sized window on the socket, because it's set if we
* exhausted the tap-side window, or if everything we receive from a
* socket is already in flight to the guest.
*
* So, if STALLED is set, and we received a window value from the tap,
* force a TCP_WINDOW_CLAMP setsockopt(). This should be investigated
* further and fixed in the kernel instead, if confirmed.
*/
if (!(conn->flags & STALLED) && conn->flags & WND_CLAMPED) {
if (prev_scaled == wnd)
return;
/* Discard +/- 1% updates to spare some syscalls. */
/* TODO: cppcheck, starting from commit b4d455df487c ("Fix
* 11349: FP negativeIndex for clamped array index (#4627)"),
* reports wnd > prev_scaled as always being true, see also:
*
* https://github.com/danmar/cppcheck/pull/4627
*
* drop this suppression once that's resolved.
*/
/* cppcheck-suppress [knownConditionTrueFalse, unmatchedSuppression] */
if ((wnd > prev_scaled && wnd * 99 / 100 < prev_scaled) ||
(wnd < prev_scaled && wnd * 101 / 100 > prev_scaled))
return;
}
conn->wnd_from_tap = MIN(wnd >> conn->ws_from_tap, USHRT_MAX);
if (setsockopt(s, SOL_TCP, TCP_WINDOW_CLAMP, &wnd, sizeof(wnd)))
trace("TCP: failed to set TCP_WINDOW_CLAMP on socket %i", s);
conn_flag(c, conn, WND_CLAMPED);
}
/**
* tcp_seq_init() - Calculate initial sequence number according to RFC 6528
* @c: Execution context
* @conn: TCP connection, with faddr, fport and eport populated
* @now: Current timestamp
*/
static void tcp_seq_init(const struct ctx *c, struct tcp_tap_conn *conn,
const struct timespec *now)
{
struct siphash_state state = SIPHASH_INIT(c->tcp.hash_secret);
union inany_addr aany;
uint64_t hash;
uint32_t ns;
if (CONN_V4(conn))
inany_from_af(&aany, AF_INET, &c->ip4.addr);
else
inany_from_af(&aany, AF_INET6, &c->ip6.addr);
inany_siphash_feed(&state, &conn->faddr);
inany_siphash_feed(&state, &aany);
hash = siphash_final(&state, 36,
(uint64_t)conn->fport << 16 | conn->eport);
/* 32ns ticks, overflows 32 bits every 137s */
ns = (now->tv_sec * 1000000000 + now->tv_nsec) >> 5;
conn->seq_to_tap = ((uint32_t)(hash >> 32) ^ (uint32_t)hash) + ns;
}
/**
* tcp_conn_pool_sock() - Get socket for new connection from pre-opened pool
* @pool: Pool of pre-opened sockets
*
* Return: socket number if available, negative code if pool is empty
*/
int tcp_conn_pool_sock(int pool[])
{
int s = -1, i;
for (i = 0; i < TCP_SOCK_POOL_SIZE; i++) {
SWAP(s, pool[i]);
if (s >= 0)
return s;
}
return -1;
}
/**
* tcp_conn_new_sock() - Open and prepare new socket for connection
* @c: Execution context
* @af: Address family
*
* Return: socket number on success, negative code if socket creation failed
*/
int tcp_conn_new_sock(const struct ctx *c, sa_family_t af)
{
int s;
s = socket(af, SOCK_STREAM | SOCK_NONBLOCK, IPPROTO_TCP);
if (s > FD_REF_MAX) {
close(s);
return -EIO;
}
if (s < 0)
return -errno;
tcp_sock_set_bufsize(c, s);
return s;
}
/**
* tcp_conn_tap_mss() - Get MSS value advertised by tap/guest
* @conn: Connection pointer
* @opts: Pointer to start of TCP options
* @optlen: Bytes in options: caller MUST ensure available length
*
* Return: clamped MSS value
*/
static uint16_t tcp_conn_tap_mss(const struct tcp_tap_conn *conn,
const char *opts, size_t optlen)
{
unsigned int mss;
int ret;
if ((ret = tcp_opt_get(opts, optlen, OPT_MSS, NULL, NULL)) < 0)
mss = MSS_DEFAULT;
else
mss = ret;
if (CONN_V4(conn))
mss = MIN(MSS4, mss);
else
mss = MIN(MSS6, mss);
return MIN(mss, USHRT_MAX);
}
/**
* tcp_bind_outbound() - Bind socket to outbound address and interface if given
* @c: Execution context
* @s: Outbound TCP socket
* @af: Address family
*/
static void tcp_bind_outbound(const struct ctx *c, int s, sa_family_t af)
{
if (af == AF_INET) {
if (!IN4_IS_ADDR_UNSPECIFIED(&c->ip4.addr_out)) {
struct sockaddr_in addr4 = {
.sin_family = AF_INET,
.sin_port = 0,
.sin_addr = c->ip4.addr_out,
};
if (bind(s, (struct sockaddr *)&addr4, sizeof(addr4))) {
debug("Can't bind IPv4 TCP socket address: %s",
strerror(errno));
}
}
if (*c->ip4.ifname_out) {
if (setsockopt(s, SOL_SOCKET, SO_BINDTODEVICE,
c->ip4.ifname_out,
strlen(c->ip4.ifname_out))) {
debug("Can't bind IPv4 TCP socket to interface:"
" %s", strerror(errno));
}
}
} else if (af == AF_INET6) {
if (!IN6_IS_ADDR_UNSPECIFIED(&c->ip6.addr_out)) {
struct sockaddr_in6 addr6 = {
.sin6_family = AF_INET6,
.sin6_port = 0,
.sin6_addr = c->ip6.addr_out,
};
if (bind(s, (struct sockaddr *)&addr6, sizeof(addr6))) {
debug("Can't bind IPv6 TCP socket address: %s",
strerror(errno));
}
}
if (*c->ip6.ifname_out) {
if (setsockopt(s, SOL_SOCKET, SO_BINDTODEVICE,
c->ip6.ifname_out,
strlen(c->ip6.ifname_out))) {
debug("Can't bind IPv6 TCP socket to interface:"
" %s", strerror(errno));
}
}
}
}
/**
* tcp_conn_from_tap() - Handle connection request (SYN segment) from tap
* @c: Execution context
* @af: Address family, AF_INET or AF_INET6
* @saddr: Source address, pointer to in_addr or in6_addr
* @daddr: Destination address, pointer to in_addr or in6_addr
* @th: TCP header from tap: caller MUST ensure it's there
* @opts: Pointer to start of options
* @optlen: Bytes in options: caller MUST ensure available length
* @now: Current timestamp
*/
static void tcp_conn_from_tap(struct ctx *c,
int af, const void *saddr, const void *daddr,
const struct tcphdr *th, const char *opts,
size_t optlen, const struct timespec *now)
{
int *pool = af == AF_INET6 ? init_sock_pool6 : init_sock_pool4;
struct sockaddr_in addr4 = {
.sin_family = AF_INET,
.sin_port = th->dest,
.sin_addr = *(struct in_addr *)daddr,
};
struct sockaddr_in6 addr6 = {
.sin6_family = AF_INET6,
.sin6_port = th->dest,
.sin6_addr = *(struct in6_addr *)daddr,
};
const struct sockaddr *sa;
struct tcp_tap_conn *conn;
socklen_t sl;
int s, mss;
(void)saddr;
if (c->tcp.conn_count >= TCP_MAX_CONNS)
return;
if ((s = tcp_conn_pool_sock(pool)) < 0)
if ((s = tcp_conn_new_sock(c, af)) < 0)
return;
if (!c->no_map_gw) {
if (af == AF_INET && IN4_ARE_ADDR_EQUAL(daddr, &c->ip4.gw))
addr4.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
if (af == AF_INET6 && IN6_ARE_ADDR_EQUAL(daddr, &c->ip6.gw))
addr6.sin6_addr = in6addr_loopback;
}
if (af == AF_INET6 && IN6_IS_ADDR_LINKLOCAL(&addr6.sin6_addr)) {
struct sockaddr_in6 addr6_ll = {
.sin6_family = AF_INET6,
.sin6_addr = c->ip6.addr_ll,
.sin6_scope_id = c->ifi6,
};
if (bind(s, (struct sockaddr *)&addr6_ll, sizeof(addr6_ll))) {
close(s);
return;
}
}
conn = CONN(c->tcp.conn_count++);
conn->c.spliced = false;
conn->sock = s;
conn->timer = -1;
conn_event(c, conn, TAP_SYN_RCVD);
conn->wnd_to_tap = WINDOW_DEFAULT;
mss = tcp_conn_tap_mss(conn, opts, optlen);
if (setsockopt(s, SOL_TCP, TCP_MAXSEG, &mss, sizeof(mss)))
trace("TCP: failed to set TCP_MAXSEG on socket %i", s);
MSS_SET(conn, mss);
tcp_get_tap_ws(conn, opts, optlen);
/* RFC 7323, 2.2: first value is not scaled. Also, don't clamp yet, to
* avoid getting a zero scale just because we set a small window now.
*/
if (!(conn->wnd_from_tap = (htons(th->window) >> conn->ws_from_tap)))
conn->wnd_from_tap = 1;
inany_from_af(&conn->faddr, af, daddr);
if (af == AF_INET) {
sa = (struct sockaddr *)&addr4;
sl = sizeof(addr4);
} else {
sa = (struct sockaddr *)&addr6;
sl = sizeof(addr6);
}
conn->fport = ntohs(th->dest);
conn->eport = ntohs(th->source);
conn->seq_init_from_tap = ntohl(th->seq);
conn->seq_from_tap = conn->seq_init_from_tap + 1;
conn->seq_ack_to_tap = conn->seq_from_tap;
tcp_seq_init(c, conn, now);
conn->seq_ack_from_tap = conn->seq_to_tap;
tcp_hash_insert(c, conn);
if (!bind(s, sa, sl)) {
tcp_rst(c, conn); /* Nobody is listening then */
return;
}
if (errno != EADDRNOTAVAIL && errno != EACCES)
conn_flag(c, conn, LOCAL);
if ((af == AF_INET && !IN4_IS_ADDR_LOOPBACK(&addr4.sin_addr)) ||
(af == AF_INET6 && !IN6_IS_ADDR_LOOPBACK(&addr6.sin6_addr) &&
!IN6_IS_ADDR_LINKLOCAL(&addr6.sin6_addr)))
tcp_bind_outbound(c, s, af);
if (connect(s, sa, sl)) {
if (errno != EINPROGRESS) {
tcp_rst(c, conn);
return;
}
tcp_get_sndbuf(conn);
} else {
tcp_get_sndbuf(conn);
if (tcp_send_flag(c, conn, SYN | ACK))
return;
conn_event(c, conn, TAP_SYN_ACK_SENT);
}
tcp_epoll_ctl(c, conn);
}
/**
* tcp_sock_consume() - Consume (discard) data from buffer
* @conn: Connection pointer
* @ack_seq: ACK sequence, host order
*
* Return: 0 on success, negative error code from recv() on failure
*/
static int tcp_sock_consume(const struct tcp_tap_conn *conn, uint32_t ack_seq)
{
/* Simply ignore out-of-order ACKs: we already consumed the data we
* needed from the buffer, and we won't rewind back to a lower ACK
* sequence.
*/
if (SEQ_LE(ack_seq, conn->seq_ack_from_tap))
return 0;
/* cppcheck-suppress [nullPointer, unmatchedSuppression] */
if (recv(conn->sock, NULL, ack_seq - conn->seq_ack_from_tap,
MSG_DONTWAIT | MSG_TRUNC) < 0)
return -errno;
return 0;
}
/**
* tcp_data_to_tap() - Finalise (queue) highest-numbered scatter-gather buffer
* @c: Execution context
* @conn: Connection pointer
* @plen: Payload length at L4
* @no_csum: Don't compute IPv4 checksum, use the one from previous buffer
* @seq: Sequence number to be sent
*/
static void tcp_data_to_tap(const struct ctx *c, struct tcp_tap_conn *conn,
ssize_t plen, int no_csum, uint32_t seq)
{
uint32_t *seq_update = &conn->seq_to_tap;
struct iovec *iov;
if (CONN_V4(conn)) {
struct tcp4_l2_buf_t *b = &tcp4_l2_buf[tcp4_l2_buf_used];
const uint16_t *check = no_csum ? &(b - 1)->iph.check : NULL;
tcp4_l2_buf_seq_update[tcp4_l2_buf_used].seq = seq_update;
tcp4_l2_buf_seq_update[tcp4_l2_buf_used].len = plen;
iov = tcp4_l2_iov + tcp4_l2_buf_used++;
iov->iov_len = tcp_l2_buf_fill_headers(c, conn, b, plen,
check, seq);
if (tcp4_l2_buf_used > ARRAY_SIZE(tcp4_l2_buf) - 1)
tcp_l2_data_buf_flush(c);
} else if (CONN_V6(conn)) {
struct tcp6_l2_buf_t *b = &tcp6_l2_buf[tcp6_l2_buf_used];
tcp6_l2_buf_seq_update[tcp6_l2_buf_used].seq = seq_update;
tcp6_l2_buf_seq_update[tcp6_l2_buf_used].len = plen;
iov = tcp6_l2_iov + tcp6_l2_buf_used++;
iov->iov_len = tcp_l2_buf_fill_headers(c, conn, b, plen,
NULL, seq);
if (tcp6_l2_buf_used > ARRAY_SIZE(tcp6_l2_buf) - 1)
tcp_l2_data_buf_flush(c);
}
}
/**
* tcp_data_from_sock() - Handle new data from socket, queue to tap, in window
* @c: Execution context
* @conn: Connection pointer
*
* Return: negative on connection reset, 0 otherwise
*
* #syscalls recvmsg
*/
static int tcp_data_from_sock(struct ctx *c, struct tcp_tap_conn *conn)
{
uint32_t wnd_scaled = conn->wnd_from_tap << conn->ws_from_tap;
int fill_bufs, send_bufs = 0, last_len, iov_rem = 0;
int sendlen, len, plen, v4 = CONN_V4(conn);
int s = conn->sock, i, ret = 0;
struct msghdr mh_sock = { 0 };
uint16_t mss = MSS_GET(conn);
uint32_t already_sent, seq;
struct iovec *iov;
already_sent = conn->seq_to_tap - conn->seq_ack_from_tap;
if (SEQ_LT(already_sent, 0)) {
/* RFC 761, section 2.1. */
trace("TCP: ACK sequence gap: ACK for %u, sent: %u",
conn->seq_ack_from_tap, conn->seq_to_tap);
conn->seq_to_tap = conn->seq_ack_from_tap;
already_sent = 0;
}
if (!wnd_scaled || already_sent >= wnd_scaled) {
conn_flag(c, conn, STALLED);
conn_flag(c, conn, ACK_FROM_TAP_DUE);
return 0;
}
/* Set up buffer descriptors we'll fill completely and partially. */
fill_bufs = DIV_ROUND_UP(wnd_scaled - already_sent, mss);
if (fill_bufs > TCP_FRAMES) {
fill_bufs = TCP_FRAMES;
iov_rem = 0;
} else {
iov_rem = (wnd_scaled - already_sent) % mss;
}
mh_sock.msg_iov = iov_sock;
mh_sock.msg_iovlen = fill_bufs + 1;
iov_sock[0].iov_base = tcp_buf_discard;
iov_sock[0].iov_len = already_sent;
if (( v4 && tcp4_l2_buf_used + fill_bufs > ARRAY_SIZE(tcp4_l2_buf)) ||
(!v4 && tcp6_l2_buf_used + fill_bufs > ARRAY_SIZE(tcp6_l2_buf))) {
tcp_l2_data_buf_flush(c);
/* Silence Coverity CWE-125 false positive */
tcp4_l2_buf_used = tcp6_l2_buf_used = 0;
}
for (i = 0, iov = iov_sock + 1; i < fill_bufs; i++, iov++) {
if (v4)
iov->iov_base = &tcp4_l2_buf[tcp4_l2_buf_used + i].data;
else
iov->iov_base = &tcp6_l2_buf[tcp6_l2_buf_used + i].data;
iov->iov_len = mss;
}
if (iov_rem)
iov_sock[fill_bufs].iov_len = iov_rem;
/* Receive into buffers, don't dequeue until acknowledged by guest. */
do
len = recvmsg(s, &mh_sock, MSG_PEEK);
while (len < 0 && errno == EINTR);
if (len < 0)
goto err;
if (!len) {
if ((conn->events & (SOCK_FIN_RCVD | TAP_FIN_SENT)) == SOCK_FIN_RCVD) {
if ((ret = tcp_send_flag(c, conn, FIN | ACK))) {
tcp_rst(c, conn);
return ret;
}
conn_event(c, conn, TAP_FIN_SENT);
}
return 0;
}
sendlen = len - already_sent;
if (sendlen <= 0) {
conn_flag(c, conn, STALLED);
return 0;
}
conn_flag(c, conn, ~STALLED);
send_bufs = DIV_ROUND_UP(sendlen, mss);
last_len = sendlen - (send_bufs - 1) * mss;
/* Likely, some new data was acked too. */
tcp_update_seqack_wnd(c, conn, 0, NULL);
/* Finally, queue to tap */
plen = mss;
seq = conn->seq_to_tap;
for (i = 0; i < send_bufs; i++) {
int no_csum = i && i != send_bufs - 1 && tcp4_l2_buf_used;
if (i == send_bufs - 1)
plen = last_len;
tcp_data_to_tap(c, conn, plen, no_csum, seq);
seq += plen;
}
conn_flag(c, conn, ACK_FROM_TAP_DUE);
return 0;
err:
if (errno != EAGAIN && errno != EWOULDBLOCK) {
ret = -errno;
tcp_rst(c, conn);
}
return ret;
}
/**
* tcp_data_from_tap() - tap/guest data for established connection
* @c: Execution context
* @conn: Connection pointer
* @p: Pool of TCP packets, with TCP headers
* @idx: Index of first data packet in pool
*
* #syscalls sendmsg
*
* Return: count of consumed packets
*/
static int tcp_data_from_tap(struct ctx *c, struct tcp_tap_conn *conn,
const struct pool *p, int idx)
{
int i, iov_i, ack = 0, fin = 0, retr = 0, keep = -1, partial_send = 0;
uint16_t max_ack_seq_wnd = conn->wnd_from_tap;
uint32_t max_ack_seq = conn->seq_ack_from_tap;
uint32_t seq_from_tap = conn->seq_from_tap;
struct msghdr mh = { .msg_iov = tcp_iov };
size_t len;
ssize_t n;
if (conn->events == CLOSED)
return p->count - idx;
ASSERT(conn->events & ESTABLISHED);
for (i = idx, iov_i = 0; i < (int)p->count; i++) {
uint32_t seq, seq_offset, ack_seq;
struct tcphdr *th;
char *data;
size_t off;
th = packet_get(p, i, 0, sizeof(*th), &len);
if (!th)
return -1;
len += sizeof(*th);
off = th->doff * 4UL;
if (off < sizeof(*th) || off > len)
return -1;
if (th->rst) {
conn_event(c, conn, CLOSED);
return 1;
}
len -= off;
data = packet_get(p, i, off, len, NULL);
if (!data)
continue;
seq = ntohl(th->seq);
ack_seq = ntohl(th->ack_seq);
if (th->ack) {
ack = 1;
if (SEQ_GE(ack_seq, conn->seq_ack_from_tap) &&
SEQ_GE(ack_seq, max_ack_seq)) {
/* Fast re-transmit */
retr = !len && !th->fin &&
ack_seq == max_ack_seq &&
ntohs(th->window) == max_ack_seq_wnd;
max_ack_seq_wnd = ntohs(th->window);
max_ack_seq = ack_seq;
}
}
if (th->fin)
fin = 1;
if (!len)
continue;
seq_offset = seq_from_tap - seq;
/* Use data from this buffer only in these two cases:
*
* , seq_from_tap , seq_from_tap
* |--------| <-- len |--------| <-- len
* '----' <-- offset ' <-- offset
* ^ seq ^ seq
* (offset >= 0, seq + len > seq_from_tap)
*
* discard in these two cases:
* , seq_from_tap , seq_from_tap
* |--------| <-- len |--------| <-- len
* '--------' <-- offset '-----| <- offset
* ^ seq ^ seq
* (offset >= 0, seq + len <= seq_from_tap)
*
* keep, look for another buffer, then go back, in this case:
* , seq_from_tap
* |--------| <-- len
* '===' <-- offset
* ^ seq
* (offset < 0)
*/
if (SEQ_GE(seq_offset, 0) && SEQ_LE(seq + len, seq_from_tap))
continue;
if (SEQ_LT(seq_offset, 0)) {
if (keep == -1)
keep = i;
continue;
}
tcp_iov[iov_i].iov_base = data + seq_offset;
tcp_iov[iov_i].iov_len = len - seq_offset;
seq_from_tap += tcp_iov[iov_i].iov_len;
iov_i++;
if (keep == i)
keep = -1;
if (keep != -1)
i = keep - 1;
}
/* On socket flush failure, pretend there was no ACK, try again later */
if (ack && !tcp_sock_consume(conn, max_ack_seq))
tcp_update_seqack_from_tap(c, conn, max_ack_seq);
tcp_clamp_window(c, conn, max_ack_seq_wnd);
if (retr) {
trace("TCP: fast re-transmit, ACK: %u, previous sequence: %u",
max_ack_seq, conn->seq_to_tap);
conn->seq_ack_from_tap = max_ack_seq;
conn->seq_to_tap = max_ack_seq;
tcp_data_from_sock(c, conn);
}
if (!iov_i)
goto out;
mh.msg_iovlen = iov_i;
eintr:
n = sendmsg(conn->sock, &mh, MSG_DONTWAIT | MSG_NOSIGNAL);
if (n < 0) {
if (errno == EPIPE) {
/* Here's the wrap, said the tap.
* In my pocket, said the socket.
* Then swiftly looked away and left.
*/
conn->seq_from_tap = seq_from_tap;
tcp_send_flag(c, conn, ACK);
}
if (errno == EINTR)
goto eintr;
if (errno == EAGAIN || errno == EWOULDBLOCK) {
tcp_send_flag(c, conn, ACK_IF_NEEDED);
return p->count - idx;
}
return -1;
}
if (n < (int)(seq_from_tap - conn->seq_from_tap)) {
partial_send = 1;
conn->seq_from_tap += n;
tcp_send_flag(c, conn, ACK_IF_NEEDED);
} else {
conn->seq_from_tap += n;
}
out:
if (keep != -1) {
/* We use an 8-bit approximation here: the associated risk is
* that we skip a duplicate ACK on 8-bit sequence number
* collision. Fast retransmit is a SHOULD in RFC 5681, 3.2.
*/
if (conn->seq_dup_ack_approx != (conn->seq_from_tap & 0xff)) {
conn->seq_dup_ack_approx = conn->seq_from_tap & 0xff;
tcp_send_flag(c, conn, DUP_ACK);
}
return p->count - idx;
}
if (ack && conn->events & TAP_FIN_SENT &&
conn->seq_ack_from_tap == conn->seq_to_tap)
conn_event(c, conn, TAP_FIN_ACKED);
if (fin && !partial_send) {
conn->seq_from_tap++;
conn_event(c, conn, TAP_FIN_RCVD);
} else {
tcp_send_flag(c, conn, ACK_IF_NEEDED);
}
return p->count - idx;
}
/**
* tcp_conn_from_sock_finish() - Complete connection setup after connect()
* @c: Execution context
* @conn: Connection pointer
* @th: TCP header of SYN, ACK segment: caller MUST ensure it's there
* @opts: Pointer to start of options
* @optlen: Bytes in options: caller MUST ensure available length
*/
static void tcp_conn_from_sock_finish(struct ctx *c, struct tcp_tap_conn *conn,
const struct tcphdr *th,
const char *opts, size_t optlen)
{
tcp_clamp_window(c, conn, ntohs(th->window));
tcp_get_tap_ws(conn, opts, optlen);
/* First value is not scaled */
if (!(conn->wnd_from_tap >>= conn->ws_from_tap))
conn->wnd_from_tap = 1;
MSS_SET(conn, tcp_conn_tap_mss(conn, opts, optlen));
conn->seq_init_from_tap = ntohl(th->seq) + 1;
conn->seq_from_tap = conn->seq_init_from_tap;
conn->seq_ack_to_tap = conn->seq_from_tap;
conn_event(c, conn, ESTABLISHED);
/* The client might have sent data already, which we didn't
* dequeue waiting for SYN,ACK from tap -- check now.
*/
tcp_data_from_sock(c, conn);
tcp_send_flag(c, conn, ACK);
}
/**
* tcp_tap_handler() - Handle packets from tap and state transitions
* @c: Execution context
* @af: Address family, AF_INET or AF_INET6
* @saddr: Source address
* @daddr: Destination address
* @p: Pool of TCP packets, with TCP headers
* @idx: Index of first packet in pool to process
* @now: Current timestamp
*
* Return: count of consumed packets
*/
int tcp_tap_handler(struct ctx *c, int af, const void *saddr, const void *daddr,
const struct pool *p, int idx, const struct timespec *now)
{
struct tcp_tap_conn *conn;
size_t optlen, len;
struct tcphdr *th;
int ack_due = 0;
char *opts;
int count;
th = packet_get(p, idx, 0, sizeof(*th), &len);
if (!th)
return 1;
len += sizeof(*th);
optlen = th->doff * 4UL - sizeof(*th);
/* Static checkers might fail to see this: */
optlen = MIN(optlen, ((1UL << 4) /* from doff width */ - 6) * 4UL);
opts = packet_get(p, idx, sizeof(*th), optlen, NULL);
conn = tcp_hash_lookup(c, af, daddr, htons(th->source), htons(th->dest));
/* New connection from tap */
if (!conn) {
if (opts && th->syn && !th->ack)
tcp_conn_from_tap(c, af, saddr, daddr, th,
opts, optlen, now);
return 1;
}
trace("TCP: packet length %lu from tap for index %lu", len, CONN_IDX(conn));
if (th->rst) {
conn_event(c, conn, CLOSED);
return 1;
}
if (th->ack && !(conn->events & ESTABLISHED))
tcp_update_seqack_from_tap(c, conn, ntohl(th->ack_seq));
/* Establishing connection from socket */
if (conn->events & SOCK_ACCEPTED) {
if (th->syn && th->ack && !th->fin) {
tcp_conn_from_sock_finish(c, conn, th, opts, optlen);
return 1;
}
goto reset;
}
/* Establishing connection from tap */
if (conn->events & TAP_SYN_RCVD) {
if (!(conn->events & TAP_SYN_ACK_SENT))
goto reset;
conn_event(c, conn, ESTABLISHED);
if (th->fin) {
conn->seq_from_tap++;
shutdown(conn->sock, SHUT_WR);
tcp_send_flag(c, conn, ACK);
conn_event(c, conn, SOCK_FIN_SENT);
return 1;
}
if (!th->ack)
goto reset;
tcp_clamp_window(c, conn, ntohs(th->window));
tcp_data_from_sock(c, conn);
if (p->count - idx == 1)
return 1;
}
/* Established connections not accepting data from tap */
if (conn->events & TAP_FIN_RCVD) {
tcp_update_seqack_from_tap(c, conn, ntohl(th->ack_seq));
if (conn->events & SOCK_FIN_RCVD &&
conn->seq_ack_from_tap == conn->seq_to_tap)
conn_event(c, conn, CLOSED);
return 1;
}
/* Established connections accepting data from tap */
count = tcp_data_from_tap(c, conn, p, idx);
if (count == -1)
goto reset;
/* Note: STALLED matters for tcp_clamp_window(): unset it only after
* processing data (and window) from the tap side
*/
conn_flag(c, conn, ~STALLED);
if (conn->seq_ack_to_tap != conn->seq_from_tap)
ack_due = 1;
if ((conn->events & TAP_FIN_RCVD) && !(conn->events & SOCK_FIN_SENT)) {
shutdown(conn->sock, SHUT_WR);
conn_event(c, conn, SOCK_FIN_SENT);
tcp_send_flag(c, conn, ACK);
ack_due = 0;
}
if (ack_due)
conn_flag(c, conn, ACK_TO_TAP_DUE);
return count;
reset:
/* Something's gone wrong, so reset the connection. We discard
* remaining packets in the batch, since they'd be invalidated when our
* RST is received, even if otherwise good.
*/
tcp_rst(c, conn);
return p->count - idx;
}
/**
* tcp_connect_finish() - Handle completion of connect() from EPOLLOUT event
* @c: Execution context
* @conn: Connection pointer
*/
static void tcp_connect_finish(struct ctx *c, struct tcp_tap_conn *conn)
{
socklen_t sl;
int so;
sl = sizeof(so);
if (getsockopt(conn->sock, SOL_SOCKET, SO_ERROR, &so, &sl) || so) {
tcp_rst(c, conn);
return;
}
if (tcp_send_flag(c, conn, SYN | ACK))
return;
conn_event(c, conn, TAP_SYN_ACK_SENT);
conn_flag(c, conn, ACK_FROM_TAP_DUE);
}
/**
* tcp_snat_inbound() - Translate source address for inbound data if needed
* @c: Execution context
* @addr: Source address of inbound packet/connection
*/
static void tcp_snat_inbound(const struct ctx *c, union inany_addr *addr)
{
struct in_addr *addr4 = inany_v4(addr);
if (addr4) {
if (IN4_IS_ADDR_LOOPBACK(addr4) ||
IN4_IS_ADDR_UNSPECIFIED(addr4) ||
IN4_ARE_ADDR_EQUAL(addr4, &c->ip4.addr_seen))
*addr4 = c->ip4.gw;
} else {
struct in6_addr *addr6 = &addr->a6;
if (IN6_IS_ADDR_LOOPBACK(addr6) ||
IN6_ARE_ADDR_EQUAL(addr6, &c->ip6.addr_seen) ||
IN6_ARE_ADDR_EQUAL(addr6, &c->ip6.addr)) {
if (IN6_IS_ADDR_LINKLOCAL(&c->ip6.gw))
*addr6 = c->ip6.gw;
else
*addr6 = c->ip6.addr_ll;
}
}
}
/**
* tcp_tap_conn_from_sock() - Initialize state for non-spliced connection
* @c: Execution context
* @ref: epoll reference of listening socket
* @conn: connection structure to initialize
* @s: Accepted socket
* @sa: Peer socket address (from accept())
* @now: Current timestamp
*/
static void tcp_tap_conn_from_sock(struct ctx *c,
union tcp_listen_epoll_ref ref,
struct tcp_tap_conn *conn, int s,
const struct sockaddr *sa,
const struct timespec *now)
{
conn->c.spliced = false;
conn->sock = s;
conn->timer = -1;
conn->ws_to_tap = conn->ws_from_tap = 0;
conn_event(c, conn, SOCK_ACCEPTED);
inany_from_sockaddr(&conn->faddr, &conn->fport, sa);
conn->eport = ref.port;
tcp_snat_inbound(c, &conn->faddr);
tcp_seq_init(c, conn, now);
tcp_hash_insert(c, conn);
conn->seq_ack_from_tap = conn->seq_to_tap;
conn->wnd_from_tap = WINDOW_DEFAULT;
tcp_send_flag(c, conn, SYN);
conn_flag(c, conn, ACK_FROM_TAP_DUE);
tcp_get_sndbuf(conn);
}
/**
* tcp_listen_handler() - Handle new connection request from listening socket
* @c: Execution context
* @ref: epoll reference of listening socket
* @now: Current timestamp
*/
void tcp_listen_handler(struct ctx *c, union epoll_ref ref,
const struct timespec *now)
{
struct sockaddr_storage sa;
socklen_t sl = sizeof(sa);
union tcp_conn *conn;
int s;
if (c->no_tcp || c->tcp.conn_count >= TCP_MAX_CONNS)
return;
s = accept4(ref.fd, (struct sockaddr *)&sa, &sl, SOCK_NONBLOCK);
if (s < 0)
return;
conn = tc + c->tcp.conn_count++;
if (c->mode == MODE_PASTA &&
tcp_splice_conn_from_sock(c, ref.tcp_listen, &conn->splice,
s, (struct sockaddr *)&sa))
return;
tcp_tap_conn_from_sock(c, ref.tcp_listen, &conn->tap, s,
(struct sockaddr *)&sa, now);
}
/**
* tcp_timer_handler() - timerfd events: close, send ACK, retransmit, or reset
* @c: Execution context
* @ref: epoll reference of timer (not connection)
*
* #syscalls timerfd_gettime
*/
void tcp_timer_handler(struct ctx *c, union epoll_ref ref)
{
struct tcp_tap_conn *conn = conn_at_idx(ref.tcp.index);
struct itimerspec check_armed = { { 0 }, { 0 } };
if (c->no_tcp || !conn)
return;
/* We don't reset timers on ~ACK_FROM_TAP_DUE, ~ACK_TO_TAP_DUE. If the
* timer is currently armed, this event came from a previous setting,
* and we just set the timer to a new point in the future: discard it.
*/
timerfd_gettime(conn->timer, &check_armed);
if (check_armed.it_value.tv_sec || check_armed.it_value.tv_nsec)
return;
if (conn->flags & ACK_TO_TAP_DUE) {
tcp_send_flag(c, conn, ACK_IF_NEEDED);
tcp_timer_ctl(c, conn);
} else if (conn->flags & ACK_FROM_TAP_DUE) {
if (!(conn->events & ESTABLISHED)) {
debug("TCP: index %li, handshake timeout", CONN_IDX(conn));
tcp_rst(c, conn);
} else if (CONN_HAS(conn, SOCK_FIN_SENT | TAP_FIN_ACKED)) {
debug("TCP: index %li, FIN timeout", CONN_IDX(conn));
tcp_rst(c, conn);
} else if (conn->retrans == TCP_MAX_RETRANS) {
debug("TCP: index %li, retransmissions count exceeded",
CONN_IDX(conn));
tcp_rst(c, conn);
} else {
debug("TCP: index %li, ACK timeout, retry", CONN_IDX(conn));
conn->retrans++;
conn->seq_to_tap = conn->seq_ack_from_tap;
tcp_data_from_sock(c, conn);
tcp_timer_ctl(c, conn);
}
} else {
struct itimerspec new = { { 0 }, { ACT_TIMEOUT, 0 } };
struct itimerspec old = { { 0 }, { 0 } };
/* Activity timeout: if it was already set, reset the
* connection, otherwise, it was a left-over from ACK_TO_TAP_DUE
* or ACK_FROM_TAP_DUE, so just set the long timeout in that
* case. This avoids having to preemptively reset the timer on
* ~ACK_TO_TAP_DUE or ~ACK_FROM_TAP_DUE.
*/
timerfd_settime(conn->timer, 0, &new, &old);
if (old.it_value.tv_sec == ACT_TIMEOUT) {
debug("TCP: index %li, activity timeout", CONN_IDX(conn));
tcp_rst(c, conn);
}
}
}
/**
* tcp_tap_sock_handler() - Handle new data from non-spliced socket
* @c: Execution context
* @conn: Connection state
* @events: epoll events bitmap
*/
static void tcp_tap_sock_handler(struct ctx *c, struct tcp_tap_conn *conn,
uint32_t events)
{
if (conn->events == CLOSED)
return;
if (events & EPOLLERR) {
tcp_rst(c, conn);
return;
}
if ((conn->events & TAP_FIN_SENT) && (events & EPOLLHUP)) {
conn_event(c, conn, CLOSED);
return;
}
if (conn->events & ESTABLISHED) {
if (CONN_HAS(conn, SOCK_FIN_SENT | TAP_FIN_ACKED))
conn_event(c, conn, CLOSED);
if (events & (EPOLLRDHUP | EPOLLHUP))
conn_event(c, conn, SOCK_FIN_RCVD);
if (events & EPOLLIN)
tcp_data_from_sock(c, conn);
if (events & EPOLLOUT)
tcp_update_seqack_wnd(c, conn, 0, NULL);
return;
}
/* EPOLLHUP during handshake: reset */
if (events & EPOLLHUP) {
tcp_rst(c, conn);
return;
}
/* Data during handshake tap-side: check later */
if (conn->events & SOCK_ACCEPTED)
return;
if (conn->events == TAP_SYN_RCVD) {
if (events & EPOLLOUT)
tcp_connect_finish(c, conn);
/* Data? Check later */
}
}
/**
* tcp_sock_handler() - Handle new data from socket, or timerfd event
* @c: Execution context
* @ref: epoll reference
* @events: epoll events bitmap
*/
void tcp_sock_handler(struct ctx *c, union epoll_ref ref, uint32_t events)
{
union tcp_conn *conn = tc + ref.tcp.index;
if (conn->c.spliced)
tcp_splice_sock_handler(c, &conn->splice, ref.fd, events);
else
tcp_tap_sock_handler(c, &conn->tap, events);
}
/**
* tcp_sock_init_af() - Initialise listening socket for a given af and port
* @c: Execution context
* @af: Address family to listen on
* @port: Port, host order
* @addr: Pointer to address for binding, NULL if not configured
* @ifname: Name of interface to bind to, NULL if not configured
*
* Return: fd for the new listening socket, negative error code on failure
*/
static int tcp_sock_init_af(const struct ctx *c, int af, in_port_t port,
const struct in_addr *addr, const char *ifname)
{
union tcp_listen_epoll_ref tref = {
.port = port + c->tcp.fwd_in.delta[port],
};
int s;
s = sock_l4(c, af, IPPROTO_TCP, addr, ifname, port, tref.u32);
if (c->tcp.fwd_in.mode == FWD_AUTO) {
if (af == AF_INET || af == AF_UNSPEC)
tcp_sock_init_ext[port][V4] = s < 0 ? -1 : s;
if (af == AF_INET6 || af == AF_UNSPEC)
tcp_sock_init_ext[port][V6] = s < 0 ? -1 : s;
}
if (s < 0)
return s;
tcp_sock_set_bufsize(c, s);
return s;
}
/**
* tcp_sock_init() - Create listening sockets for a given host ("inbound") port
* @c: Execution context
* @af: Address family to select a specific IP version, or AF_UNSPEC
* @addr: Pointer to address for binding, NULL if not configured
* @ifname: Name of interface to bind to, NULL if not configured
* @port: Port, host order
*
* Return: 0 on (partial) success, negative error code on (complete) failure
*/
int tcp_sock_init(const struct ctx *c, sa_family_t af, const void *addr,
const char *ifname, in_port_t port)
{
int r4 = FD_REF_MAX + 1, r6 = FD_REF_MAX + 1;
if (af == AF_UNSPEC && c->ifi4 && c->ifi6)
/* Attempt to get a dual stack socket */
if (tcp_sock_init_af(c, AF_UNSPEC, port, addr, ifname) >= 0)
return 0;
/* Otherwise create a socket per IP version */
if ((af == AF_INET || af == AF_UNSPEC) && c->ifi4)
r4 = tcp_sock_init_af(c, AF_INET, port, addr, ifname);
if ((af == AF_INET6 || af == AF_UNSPEC) && c->ifi6)
r6 = tcp_sock_init_af(c, AF_INET6, port, addr, ifname);
if (IN_INTERVAL(0, FD_REF_MAX, r4) || IN_INTERVAL(0, FD_REF_MAX, r6))
return 0;
return r4 < 0 ? r4 : r6;
}
/**
* tcp_ns_sock_init4() - Init socket to listen for outbound IPv4 connections
* @c: Execution context
* @port: Port, host order
*/
static void tcp_ns_sock_init4(const struct ctx *c, in_port_t port)
{
union tcp_listen_epoll_ref tref = {
.port = port + c->tcp.fwd_out.delta[port],
.ns = true,
};
struct in_addr loopback = { htonl(INADDR_LOOPBACK) };
int s;
ASSERT(c->mode == MODE_PASTA);
s = sock_l4(c, AF_INET, IPPROTO_TCP, &loopback, NULL, port, tref.u32);
if (s >= 0)
tcp_sock_set_bufsize(c, s);
else
s = -1;
if (c->tcp.fwd_out.mode == FWD_AUTO)
tcp_sock_ns[port][V4] = s;
}
/**
* tcp_ns_sock_init6() - Init socket to listen for outbound IPv6 connections
* @c: Execution context
* @port: Port, host order
*/
static void tcp_ns_sock_init6(const struct ctx *c, in_port_t port)
{
union tcp_listen_epoll_ref tref = {
.port = port + c->tcp.fwd_out.delta[port],
.ns = true,
};
int s;
ASSERT(c->mode == MODE_PASTA);
s = sock_l4(c, AF_INET6, IPPROTO_TCP, &in6addr_loopback, NULL, port,
tref.u32);
if (s >= 0)
tcp_sock_set_bufsize(c, s);
else
s = -1;
if (c->tcp.fwd_out.mode == FWD_AUTO)
tcp_sock_ns[port][V6] = s;
}
/**
* tcp_ns_sock_init() - Init socket to listen for spliced outbound connections
* @c: Execution context
* @port: Port, host order
*/
void tcp_ns_sock_init(const struct ctx *c, in_port_t port)
{
if (c->ifi4)
tcp_ns_sock_init4(c, port);
if (c->ifi6)
tcp_ns_sock_init6(c, port);
}
/**
* tcp_ns_socks_init() - Bind sockets in namespace for outbound connections
* @arg: Execution context
*
* Return: 0
*/
static int tcp_ns_socks_init(void *arg)
{
struct ctx *c = (struct ctx *)arg;
unsigned port;
ns_enter(c);
for (port = 0; port < NUM_PORTS; port++) {
if (!bitmap_isset(c->tcp.fwd_out.map, port))
continue;
tcp_ns_sock_init(c, port);
}
return 0;
}
/**
* tcp_sock_refill_pool() - Refill one pool of pre-opened sockets
* @c: Execution context
* @pool: Pool of sockets to refill
* @af: Address family to use
*/
void tcp_sock_refill_pool(const struct ctx *c, int pool[], int af)
{
int i;
for (i = 0; i < TCP_SOCK_POOL_SIZE; i++) {
if (pool[i] >= 0)
break;
pool[i] = tcp_conn_new_sock(c, af);
}
}
/**
* tcp_sock_refill_init() - Refill pools of pre-opened sockets in init ns
* @c: Execution context
*/
static void tcp_sock_refill_init(const struct ctx *c)
{
if (c->ifi4)
tcp_sock_refill_pool(c, init_sock_pool4, AF_INET);
if (c->ifi6)
tcp_sock_refill_pool(c, init_sock_pool6, AF_INET6);
}
/**
* tcp_init() - Get initial sequence, hash secret, initialise per-socket data
* @c: Execution context
*
* Return: 0, doesn't return on failure
*/
int tcp_init(struct ctx *c)
{
int i;
#ifndef HAS_GETRANDOM
int dev_random = open("/dev/random", O_RDONLY);
unsigned int random_read = 0;
while (dev_random && random_read < sizeof(c->tcp.hash_secret)) {
int ret = read(dev_random,
(uint8_t *)&c->tcp.hash_secret + random_read,
sizeof(c->tcp.hash_secret) - random_read);
if (ret == -1 && errno == EINTR)
continue;
if (ret <= 0)
break;
random_read += ret;
}
if (dev_random >= 0)
close(dev_random);
if (random_read < sizeof(c->tcp.hash_secret)) {
#else
if (getrandom(&c->tcp.hash_secret, sizeof(c->tcp.hash_secret),
GRND_RANDOM) < 0) {
#endif /* !HAS_GETRANDOM */
perror("TCP initial sequence getrandom");
exit(EXIT_FAILURE);
}
for (i = 0; i < ARRAY_SIZE(tcp_l2_mh); i++)
tcp_l2_mh[i] = (struct mmsghdr) { .msg_hdr.msg_iovlen = 1 };
if (c->ifi4)
tcp_sock4_iov_init(c);
if (c->ifi6)
tcp_sock6_iov_init(c);
memset(init_sock_pool4, 0xff, sizeof(init_sock_pool4));
memset(init_sock_pool6, 0xff, sizeof(init_sock_pool6));
memset(tcp_sock_init_ext, 0xff, sizeof(tcp_sock_init_ext));
memset(tcp_sock_ns, 0xff, sizeof(tcp_sock_ns));
tcp_sock_refill_init(c);
if (c->mode == MODE_PASTA) {
tcp_splice_init(c);
NS_CALL(tcp_ns_socks_init, c);
}
return 0;
}
/**
* struct tcp_port_rebind_arg - Arguments for tcp_port_rebind()
* @c: Execution context
* @bind_in_ns: Rebind ports in namespace, not in init
*/
struct tcp_port_rebind_arg {
struct ctx *c;
int bind_in_ns;
};
/**
* tcp_port_rebind() - Rebind ports in namespace or init
* @arg: See struct tcp_port_rebind_arg
*
* Return: 0
*/
static int tcp_port_rebind(void *arg)
{
struct tcp_port_rebind_arg *a = (struct tcp_port_rebind_arg *)arg;
unsigned port;
if (a->bind_in_ns) {
ns_enter(a->c);
for (port = 0; port < NUM_PORTS; port++) {
if (!bitmap_isset(a->c->tcp.fwd_out.map, port)) {
if (tcp_sock_ns[port][V4] >= 0) {
close(tcp_sock_ns[port][V4]);
tcp_sock_ns[port][V4] = -1;
}
if (tcp_sock_ns[port][V6] >= 0) {
close(tcp_sock_ns[port][V6]);
tcp_sock_ns[port][V6] = -1;
}
continue;
}
/* Don't loop back our own ports */
if (bitmap_isset(a->c->tcp.fwd_in.map, port))
continue;
if ((a->c->ifi4 && tcp_sock_ns[port][V4] == -1) ||
(a->c->ifi6 && tcp_sock_ns[port][V6] == -1))
tcp_ns_sock_init(a->c, port);
}
} else {
for (port = 0; port < NUM_PORTS; port++) {
if (!bitmap_isset(a->c->tcp.fwd_in.map, port)) {
if (tcp_sock_init_ext[port][V4] >= 0) {
close(tcp_sock_init_ext[port][V4]);
tcp_sock_init_ext[port][V4] = -1;
}
if (tcp_sock_init_ext[port][V6] >= 0) {
close(tcp_sock_init_ext[port][V6]);
tcp_sock_init_ext[port][V6] = -1;
}
continue;
}
/* Don't loop back our own ports */
if (bitmap_isset(a->c->tcp.fwd_out.map, port))
continue;
if ((a->c->ifi4 && tcp_sock_init_ext[port][V4] == -1) ||
(a->c->ifi6 && tcp_sock_init_ext[port][V6] == -1))
tcp_sock_init(a->c, AF_UNSPEC, NULL, NULL,
port);
}
}
return 0;
}
/**
* tcp_timer() - Periodic tasks: port detection, closed connections, pool refill
* @c: Execution context
* @ts: Unused
*/
void tcp_timer(struct ctx *c, const struct timespec *ts)
{
union tcp_conn *conn;
(void)ts;
if (c->mode == MODE_PASTA) {
struct tcp_port_rebind_arg rebind_arg = { c, 0 };
if (c->tcp.fwd_out.mode == FWD_AUTO) {
get_bound_ports_tcp(c, 0);
rebind_arg.bind_in_ns = 1;
NS_CALL(tcp_port_rebind, &rebind_arg);
}
if (c->tcp.fwd_in.mode == FWD_AUTO) {
get_bound_ports_tcp(c, 1);
rebind_arg.bind_in_ns = 0;
tcp_port_rebind(&rebind_arg);
}
}
for (conn = tc + c->tcp.conn_count - 1; conn >= tc; conn--) {
if (conn->c.spliced) {
tcp_splice_timer(c, conn);
} else {
if (conn->tap.events == CLOSED)
tcp_conn_destroy(c, conn);
}
}
tcp_sock_refill_init(c);
if (c->mode == MODE_PASTA)
tcp_splice_refill(c);
}
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