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passt/tcp.c
Stefano Brivio d2272f74f7 tcp: Proper error handling for sendmmsg() to UNIX domain socket 
As data from socket is forwarded to the guest, sendmmsg() might send
fewer bytes than requested in three different ways:

- failing altogether with a negative error code -- ignore that,
  we'll get an error on the UNIX domain socket later if there's
  really an issue with it and reset the connection to the guest

- sending less than 'vlen' messages -- instead of assuming success
  in that case and waiting for the guest to send a duplicate ACK
  indicating missing data, update the sequence number according to
  what was actually sent and spare some retransmissions

- somewhat unexpectedly to me, sending 'vlen' or less than 'vlen'
  messages, returning up to 'vlen', with the last message being
  partially sent, and no further indication of errors other than
  the returned msg_len for the last partially sent message being
  less than iov_len.

  In this case, we would assume success and proceed as nothing
  happened. However, qemu would fail to parse any further message,
  having received a partial descriptor, and eventually close the
  connection, logging:

	serious error: oversized packet received,connection terminated.

  as the length descriptor for the next message would be sourced
  from the middle of the next successfully sent message, not from
  its header.

  Handle this by checking the msg_len returned for the last (even
  partially) sent message, and force re-sending the missing bytes,
  if any, with a blocking sendmsg() -- qemu must not receive
  anything else than that anyway.

While at it, allow to send up to 64KiB for each message, the
previous 32KiB limit isn't actually required, and just switch to a
new message at each iteration on sending buffers, they are already
MSS-sized anyway, so the check in the loop isn't really needed.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
2021-08-26 23:30:22 +02:00

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// SPDX-License-Identifier: AGPL-3.0-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) 2020-2021 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 states 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
* - TODO: sequence collision attacks
*
* 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 MAX_TAP_CONNS below (currently 1M, close to
* the maximum amount of file descriptors typically available to a process on
* Linux).
*
* While fragmentation and reassembly are not implemented, tracking of missing
* segments and retransmissions needs to be, thus data needs to linger on
* sockets as long as it's not acknowledged by the guest, and read using
* MSG_PEEK into a single, preallocated static buffer sized to the maximum
* supported window, 16MiB. This imposes a practical limitation on window
* scaling, that is, the maximum factor is 512. If a bigger window scaling
* factor is observed during connection establishment, connection is reset and
* reestablished by omitting the scaling factor in the SYN segment. This
* limitation only applies to the window scaling advertised by the guest, but
* if exceeded, no window scaling will be allowed at all toward either endpoint.
*
*
* 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 the @tt array of struct tcp_tap_conn, 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 @tt 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.
*
*
* States and events
* -----------------
*
* These states apply to connected sockets only, listening sockets are always
* open after initialisation, in LISTEN state. A single state is maintained for
* both sides of the connection, and some states are omitted as they are already
* handled by host kernel and guest.
*
* - CLOSED no connection
* No associated events: this is always a final state, new connections
* directly start from TAP_SYN_SENT or SOCK_SYN_SENT described below.
*
* - TAP_SYN_SENT connect() in progress, triggered from tap
* - connect() completes SYN,ACK to tap > TAP_SYN_RCVD
* - connect() aborts RST to tap, close socket > CLOSED
* - RST from tap close socket > CLOSED
*
* - SOCK_SYN_SENT new connected socket, SYN sent to tap
* - SYN,ACK from tap ACK to tap > ESTABLISHED
* - socket error RST to tap, close socket > CLOSED
* - SYN,ACK timeout RST to tap, close socket > CLOSED
* - RST from tap close socket > CLOSED
*
* - TAP_SYN_RCVD connect() completed, SYN,ACK sent to tap
* - FIN from tap write shutdown > FIN_WAIT_1
* - ACK from tap > ESTABLISHED
* - socket error RST to tap, close socket > CLOSED
* - ACK timeout RST to tap, close socket > CLOSED
* - RST from tap close socket > CLOSED
*
* - ESTABLISHED connection established, ready for data
* - FIN from tap write shutdown > FIN_WAIT_1
* - zero-sized socket read read shutdown, FIN to tap > ESTABLISHED_SOCK_FIN
* - socket error RST to tap, close socket > CLOSED
* - data timeout FIN to tap > ESTABLISHED_SOCK_FIN
* - RST from tap close socket > CLOSED
*
* - ESTABLISHED_SOCK_FIN socket closing connection, FIN sent to tap
* - ACK from tap > CLOSE_WAIT
* - ACK timeout RST to tap, close socket > CLOSED
* - RST from tap close socket > CLOSED
*
* - CLOSE_WAIT socket closing connection, ACK from tap
* - FIN from tap write shutdown > LAST_ACK
* - socket error RST to tap, close socket > CLOSED
* - FIN timeout RST to tap, close socket > CLOSED
* - RST from tap close socket > CLOSED
*
* - LAST_ACK socket started close, tap completed it
* - anything from socket close socket > CLOSED
* - socket error RST to tap, close socket > CLOSED
* - ACK timeout RST to tap, close socket > CLOSED
* - RST from tap close socket > CLOSED
*
* - FIN_WAIT_1 tap closing connection, FIN sent to socket
* - zero-sized socket read FIN,ACK to tap, shutdown > FIN_WAIT_1_SOCK_FIN
* - socket error RST to tap, close socket > CLOSED
* - ACK timeout RST to tap, close socket > CLOSED
* - RST from tap close socket > CLOSED
*
* - FIN_WAIT_1_SOCK_FIN tap closing connection, FIN received from socket
* - ACK from tap close socket > CLOSED
* - socket error RST to tap, close socket > CLOSED
* - ACK timeout RST to tap, close socket > CLOSED
* - RST from tap close socket > 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
* -----------------
*
* A bitmap of TCP_MAX_CONNS bits indicate the connections subject to timed
* events based on states:
* - SOCK_SYN_SENT: after a 2MSL (240s) timeout waiting for a SYN,ACK segment
* from tap expires, connection is reset (RST to tap, socket closed)
* - TAP_SYN_RCVD: after a 2MSL (240s) timeout waiting for an ACK segment from
* tap expires, connection is reset (RST to tap, socket closed)
* - TAP_SYN_SENT: connect() is pending, timeout is handled implicitly by
* connect() timeout, connection will be reset in case
* - ESTABLISHED, ESTABLISHED_SOCK_FIN: if an ACK segment to tap is pending,
* bytes acknowledged by socket endpoint are checked every 50ms (one quarter
* of current TCP_DELACK_MAX on Linux)
* - ESTABLISHED, ESTABLISHED_SOCK_FIN: after a timeout of 3s (TODO: implement
* requirements from RFC 6298) waiting for an ACK segment from tap expires,
* data from socket queue is retransmitted starting from the last ACK sequence
* - ESTABLISHED, ESTABLISHED_SOCK_FIN: after a two hours (current
* TCP_KEEPALIVE_TIME on Linux) timeout waiting for any activity expires,
* connection is reset (RST to tap, socket closed)
* - ESTABLISHED_SOCK_FIN: after a 2MSL (240s) timeout waiting for an ACK
* segment from tap expires, connection is reset (RST to tap, socket closed)
* - CLOSE_WAIT: after a 2MSL (240s) timeout waiting for a FIN segment from tap
* expires, connection is reset (RST to tap, socket closed)
* - FIN_WAIT_1: after a 2MSL (240s) timeout waiting for an ACK segment from
* socet expires, connection is reset (RST to tap, socket closed)
* - FIN_WAIT_1_SOCK_FIN: after a 2MSL (240s) timeout waiting for an ACK segment
* from tap expires, connection is reset (RST to tap, socket closed)
* - LAST_ACK: after a 2MSL (240s) timeout waiting for an ACK segment from
* socket expires, connection is reset (RST to tap, socket closed)
*
*
* Data flows (from ESTABLISHED, ESTABLISHED_SOCK_FIN states)
* ----------------------------------------------------------
*
* @seq_to_tap: next sequence for packets to tap
* @seq_ack_from_tap: last ACK number received from tap
* @seq_from_tap: next sequence for packets from tap (not actually sent)
* @seq_ack_to_tap: last ACK number sent to tap
*
* @seq_init_from_tap: initial sequence number from tap
*
* @tap_window: last window size received from tap, scaled
* @tcpi_acked_last: most recent value of tcpi_bytes_acked (TCP_INFO)
*
* - from socket to tap:
* - on new data from socket:
* - peek into buffer
* - send data to tap:
* - 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 <= @tap_window)
* - mark socket in bitmap for periodic ACK check, set @last_ts_to_tap
* - on read error, send RST to tap, close socket
* - on zero read, send FIN to tap, enter ESTABLISHED_SOCK_FIN
* - on ACK from tap:
* - set @ts_ack_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
* - on @seq_ack_from_tap == @seq_to_tap, mark in bitmap, umark otherwise
* - periodically:
* - if @seq_ack_from_tap < @seq_to_tap and the retransmission timer
* (TODO: implement requirements from RFC 6298, currently 3s fixed) from
* @ts_sock elapsed, reset @seq_to_tap to @seq_ack_from_tap, and
* resend data with the steps listed above
*
* - from tap to socket:
* - on packet from tap:
* - set @ts_tap
* - 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
* - query socket for TCP_INFO, on tcpi_bytes_acked > @tcpi_acked_last,
* set @tcpi_acked_last to tcpi_bytes_acked, set @seq_ack_to_tap
* to (tcpi_bytes_acked + @seq_init_from_tap) % 2^32 and
* send ACK to tap
* - periodically:
* - query socket for TCP_INFO, on tcpi_bytes_acked > @tcpi_acked_last,
* set @tcpi_acked_last to tcpi_bytes_acked, set @seq_ack_to_tap
* to (tcpi_bytes_acked + @seq_init_from_tap) % 2^32 and
* send ACK to tap
*
*
* 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, the implementation is substantially simpler: packets are directly
* translated between L4 sockets using a pair of splice() syscalls. These
* connections are tracked in the @ts array of struct tcp_splice_conn, using
* just four states:
*
* - CLOSED: no connection
* - SPLICE_ACCEPTED: accept() on the listening socket succeeded
* - SPLICE_CONNECT: connect() issued in the destination namespace
* - SPLICE_ESTABLISHED: connect() succeeded, packets are transferred
*/
#define _GNU_SOURCE
#include <sched.h>
#include <fcntl.h>
#include <stdio.h>
#include <errno.h>
#include <limits.h>
#include <net/ethernet.h>
#include <net/if.h>
#include <netinet/in.h>
#include <stdint.h>
#include <stddef.h>
#include <string.h>
#include <sys/epoll.h>
#include <sys/random.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/tcp.h>
#include <time.h>
#include "checksum.h"
#include "util.h"
#include "passt.h"
#include "tap.h"
#include "siphash.h"
#include "pcap.h"
#define MAX_TAP_CONNS (128 * 1024)
#define MAX_SPLICE_CONNS (128 * 1024)
#define TCP_TAP_FRAMES 32
#define PIPE_SIZE (1024 * 1024)
#define TCP_HASH_TABLE_LOAD 70 /* % */
#define TCP_HASH_TABLE_SIZE (MAX_TAP_CONNS * 100 / \
TCP_HASH_TABLE_LOAD)
#define MAX_WS 9
#define MAX_WINDOW (1 << (16 + (MAX_WS)))
#define MSS_DEFAULT 536
#define WINDOW_DEFAULT 14600 /* RFC 6928 */
#define SYN_TIMEOUT 240000 /* ms */
#define ACK_TIMEOUT 2000
#define ACK_INTERVAL 50
#define ACT_TIMEOUT 7200000
#define FIN_TIMEOUT 240000
#define LAST_ACK_TIMEOUT 240000
/* 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
enum tcp_state {
CLOSED = 0,
TAP_SYN_SENT,
SOCK_SYN_SENT,
TAP_SYN_RCVD,
ESTABLISHED,
ESTABLISHED_SOCK_FIN,
CLOSE_WAIT,
LAST_ACK,
FIN_WAIT_1,
FIN_WAIT_1_SOCK_FIN,
SPLICE_ACCEPTED,
SPLICE_CONNECT,
SPLICE_ESTABLISHED,
};
#define TCP_STATE_STR_SIZE (SPLICE_ESTABLISHED + 1)
static char *tcp_state_str[TCP_STATE_STR_SIZE] __attribute((__unused__)) = {
"CLOSED", "TAP_SYN_SENT", "SOCK_SYN_SENT", "TAP_SYN_RCVD",
"ESTABLISHED", "ESTABLISHED_SOCK_FIN", "CLOSE_WAIT", "LAST_ACK",
"FIN_WAIT_1", "FIN_WAIT_1_SOCK_FIN",
"SPLICE_ACCEPTED", "SPLICE_CONNECT", "SPLICE_ESTABLISHED",
};
#define FIN (1 << 0)
#define SYN (1 << 1)
#define RST (1 << 2)
#define ACK (1 << 4)
/* Flags for internal usage */
#define ZERO_WINDOW (1 << 5)
#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
struct tcp_tap_conn;
/**
* struct tcp_tap_conn - Descriptor for a TCP connection via tap (not spliced)
* @next: Pointer to next item in hash chain, if any
* @sock: Socket descriptor number
* @hash_bucket: Bucket index in connection lookup hash table
* @a.a6: IPv6 remote address, can be IPv4-mapped
* @a.a4.zero: Zero prefix for IPv4-mapped, see RFC 6890, Table 20
* @a.a4.one: Ones prefix for IPv4-mapped
* @a.a4.a: IPv4 address
* @tap_port: Guest-facing tap port
* @sock_port: Remote, socket-facing port
* @state: TCP connection state
* @seq_to_tap: Next sequence for packets to tap
* @seq_ack_from_tap: Last ACK number received from tap
* @seq_from_tap: Next sequence for packets from tap (not actually sent)
* @seq_ack_to_tap: Last ACK number sent to tap
* @seq_init_from_tap: Initial sequence number from tap
* @tcpi_acked_last: Most recent value of tcpi_bytes_acked (TCP_INFO query)
* @ws_allowed: Window scaling allowed
* @ws: Window scaling factor
* @tap_window: Last window size received from tap, scaled
* @window_clamped: Window was clamped on socket at least once
* @no_snd_wnd: Kernel won't report window (without commit 8f7baad7f035)
* @tcpi_acked_last: Most recent value of tcpi_snd_wnd (TCP_INFO query)
* @ts_sock: Last activity timestamp from socket for timeout purposes
* @ts_tap: Last activity timestamp from tap for timeout purposes
* @ts_ack_tap: Last ACK segment timestamp from tap for timeout purposes
* @mss_guest: Maximum segment size advertised by guest
*/
struct tcp_tap_conn {
struct tcp_tap_conn *next;
int sock;
int hash_bucket;
union {
struct in6_addr a6;
struct {
uint8_t zero[10];
uint8_t one[2];
struct in_addr a;
} a4;
} a;
in_port_t tap_port;
in_port_t sock_port;
enum tcp_state state;
uint32_t seq_to_tap;
uint32_t seq_ack_from_tap;
uint32_t seq_from_tap;
uint32_t seq_ack_to_tap;
uint32_t seq_init_from_tap;
uint32_t seq_init_to_tap;
uint64_t tcpi_acked_last;
int ws_allowed;
int ws;
uint32_t tap_window;
int window_clamped;
int no_snd_wnd;
uint32_t tcpi_snd_wnd;
struct timespec ts_sock;
struct timespec ts_tap;
struct timespec ts_ack_tap;
int mss_guest;
};
/**
* struct tcp_splice_conn - Descriptor for a spliced TCP connection
* @from: File descriptor number of socket for accepted connection
* @pipe_from_to: Pipe ends for splice() from @from to @to
* @to: File descriptor number of peer connected socket
* @pipe_to_from: Pipe ends for splice() from @to to @from
* @state: TCP connection state
*/
struct tcp_splice_conn {
int from;
int pipe_from_to[2];
int to;
int pipe_to_from[2];
enum tcp_state state;
int v6;
};
/* Static buffers */
/**
* tcp4_l2_buf_t - Pre-cooked IPv4 packet buffers for tap connections
* @psum: Partial IP header checksum (excluding tot_len and saddr)
* @psum: Partial TCP header checksum (excluding length and saddr)
* @vnet_len: 4-byte qemu vnet buffer length descriptor, only for passt mode
* @eh: Pre-filled Ethernet header
* @iph: Pre-filled IP header (except for tot_len and saddr)
* @uh: Headroom for TCP header
* @data: Storage for TCP payload
*/
__extension__ static struct tcp4_l2_buf_t {
uint32_t psum; /* 0 */
uint32_t tsum; /* 4 */
#ifdef __AVX2__
uint8_t pad[18]; /* 8, align th to 32 bytes */
#endif
uint32_t vnet_len; /* 26 */
struct ethhdr eh; /* 30 */
struct iphdr iph; /* 44 */
struct tcphdr th; /* 64 */
uint8_t data[USHRT_MAX - sizeof(struct tcphdr)];
#ifdef __AVX2__
} __attribute__ ((packed, aligned(32)))
#else
} __attribute__ ((packed, aligned(__alignof__(unsigned int))))
#endif
tcp4_l2_buf[TCP_TAP_FRAMES] = {
[ 0 ... TCP_TAP_FRAMES - 1 ] = {
0, 0,
#ifdef __AVX2__
{ 0 },
#endif
0, L2_BUF_ETH_IP4_INIT, L2_BUF_IP4_INIT(IPPROTO_TCP),
{ .doff = sizeof(struct tcphdr) / 4, .ack = 1 }, { 0 },
},
};
static int tcp4_l2_buf_mss;
static int tcp4_l2_buf_mss_nr_set;
static int tcp4_l2_buf_mss_tap;
static int tcp4_l2_buf_mss_tap_nr_set;
/**
* tcp6_l2_buf_t - Pre-cooked IPv6 packet buffers for tap connections
* @vnet_len: 4-byte qemu vnet buffer length descriptor, only for passt mode
* @eh: Pre-filled Ethernet header
* @ip6h: Pre-filled IP header (except for payload_len and addresses)
* @th: Headroom for TCP header
* @data: Storage for TCP payload
*/
__extension__ 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
uint32_t vnet_len; /* 14 2 */
struct ethhdr eh; /* 18 6 */
struct ipv6hdr ip6h; /* 32 20 */
struct tcphdr th; /* 72 60 */
uint8_t data[USHRT_MAX -
(sizeof(struct ipv6hdr) + sizeof(struct tcphdr))];
#ifdef __AVX2__
} __attribute__ ((packed, aligned(32)))
#else
} __attribute__ ((packed, aligned(__alignof__(unsigned int))))
#endif
tcp6_l2_buf[TCP_TAP_FRAMES] = {
[ 0 ... TCP_TAP_FRAMES - 1 ] = {
{ 0 },
0, L2_BUF_ETH_IP6_INIT, L2_BUF_IP6_INIT(IPPROTO_TCP),
{ .doff = sizeof(struct tcphdr) / 4, .ack = 1 }, { 0 },
},
};
static int tcp6_l2_buf_mss;
static int tcp6_l2_buf_mss_nr_set;
static int tcp6_l2_buf_mss_tap;
static int tcp6_l2_buf_mss_tap_nr_set;
/* recvmmsg()/sendmmsg() data for tap */
static struct iovec tcp4_l2_iov_sock [TCP_TAP_FRAMES + 1];
static struct iovec tcp6_l2_iov_sock [TCP_TAP_FRAMES + 1];
static char tcp_buf_discard [MAX_WINDOW];
static struct iovec tcp4_l2_iov_tap [TCP_TAP_FRAMES];
static struct iovec tcp6_l2_iov_tap [TCP_TAP_FRAMES];
static struct msghdr tcp4_l2_mh_sock;
static struct msghdr tcp6_l2_mh_sock;
__extension__
static struct mmsghdr tcp_l2_mh_tap [TCP_TAP_FRAMES] = {
[ 0 ... TCP_TAP_FRAMES - 1 ] = {
.msg_hdr.msg_iovlen = 1,
},
};
/* sendmsg() to socket */
static struct iovec tcp_tap_iov [TAP_MSGS];
/* Bitmap, activity monitoring needed for connection via tap */
static uint8_t tcp_act[MAX_TAP_CONNS / 8] = { 0 };
/* TCP connections */
static struct tcp_tap_conn tt[MAX_TAP_CONNS];
static struct tcp_splice_conn ts[MAX_SPLICE_CONNS];
/* Table for lookup from remote address, local port, remote port */
static struct tcp_tap_conn *tt_hash[TCP_HASH_TABLE_SIZE];
/**
* tcp_tap_state() - Set given TCP state for tap connection, report to stderr
* @conn: Connection pointer
* @state: New TCP state to be set
*/
static void tcp_tap_state(struct tcp_tap_conn *conn, enum tcp_state state)
{
debug("TCP: socket %i: %s -> %s",
conn->sock, tcp_state_str[conn->state], tcp_state_str[state]);
conn->state = state;
}
/**
* tcp_splice_state() - Set state for spliced connection, report to stderr
* @conn: Connection pointer
* @state: New TCP state to be set
*/
static void tcp_splice_state(struct tcp_splice_conn *conn, enum tcp_state state)
{
debug("TCP: index %i: %s -> %s",
conn - ts, tcp_state_str[conn->state], tcp_state_str[state]);
conn->state = state;
}
/**
* 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 = buf->psum;
sum += buf->iph.tot_len;
sum += (buf->iph.saddr >> 16) & 0xffff;
sum += buf->iph.saddr & 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 = buf->tsum;
sum += (buf->iph.saddr >> 16) & 0xffff;
sum += buf->iph.saddr & 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
* @ip_da: Pointer to IPv4 destination address, NULL if unchanged
*/
void tcp_update_l2_buf(unsigned char *eth_d, unsigned char *eth_s,
uint32_t *ip_da)
{
int i;
for (i = 0; i < TCP_TAP_FRAMES; i++) {
struct tcp4_l2_buf_t *b4 = &tcp4_l2_buf[i];
struct tcp6_l2_buf_t *b6 = &tcp6_l2_buf[i];
if (eth_d) {
memcpy(b4->eh.h_dest, eth_d, ETH_ALEN);
memcpy(b6->eh.h_dest, eth_d, ETH_ALEN);
}
if (eth_s) {
memcpy(b4->eh.h_source, eth_s, ETH_ALEN);
memcpy(b6->eh.h_source, eth_s, ETH_ALEN);
}
if (ip_da) {
b4->iph.daddr = *ip_da;
if (!i) {
b4->iph.saddr = 0;
b4->iph.tot_len = 0;
b4->iph.check = 0;
b4->psum = sum_16b(&b4->iph, 20);
b4->tsum = ((*ip_da >> 16) & 0xffff) +
(*ip_da & 0xffff) +
htons(IPPROTO_TCP);
} else {
b4->psum = tcp4_l2_buf[0].psum;
b4->tsum = tcp4_l2_buf[0].tsum;
}
}
}
}
/**
* tcp_sock4_iov_init() - Initialise scatter-gather L2 buffers for IPv4 sockets
*/
static void tcp_sock4_iov_init(void)
{
struct iovec *iov;
int i;
tcp4_l2_iov_sock[0].iov_base = tcp_buf_discard;
for (i = 0, iov = tcp4_l2_iov_sock + 1; i < TCP_TAP_FRAMES;
i++, iov++) {
iov->iov_base = &tcp4_l2_buf[i].data;
iov->iov_len = MSS_DEFAULT;
}
tcp4_l2_mh_sock.msg_iov = tcp4_l2_iov_sock;
for (i = 0, iov = tcp4_l2_iov_tap; i < TCP_TAP_FRAMES; i++, iov++) {
iov->iov_base = &tcp4_l2_buf[i].vnet_len;
iov->iov_len = MSS_DEFAULT;
}
}
/**
* tcp_sock6_iov_init() - Initialise scatter-gather L2 buffers for IPv6 sockets
*/
static void tcp_sock6_iov_init(void)
{
struct iovec *iov;
int i;
tcp6_l2_iov_sock[0].iov_base = tcp_buf_discard;
for (i = 0, iov = tcp6_l2_iov_sock + 1; i < TCP_TAP_FRAMES;
i++, iov++) {
iov->iov_base = &tcp6_l2_buf[i].data;
iov->iov_len = MSS_DEFAULT;
}
tcp6_l2_mh_sock.msg_iov = tcp6_l2_iov_sock;
for (i = 0, iov = tcp6_l2_iov_tap; i < TCP_TAP_FRAMES; i++, iov++) {
iov->iov_base = &tcp6_l2_buf[i].vnet_len;
iov->iov_len = MSS_DEFAULT;
}
}
/**
* tcp_opt_get() - Get option, and value if any, from TCP header
* @th: Pointer to TCP header
* @len: Length of buffer, including TCP header
* @__type: Option type to look for
* @__optlen: Optional, filled with option length if passed
* @__value: 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(struct tcphdr *th, size_t len, uint8_t __type,
uint8_t *__optlen, char **__value)
{
uint8_t type, optlen;
char *p;
if (len > th->doff * 4)
len = th->doff * 4;
len -= sizeof(*th);
p = (char *)(th + 1);
for (; len >= 2; p += optlen, len -= optlen) {
switch (*p) {
case OPT_EOL:
return -1;
case OPT_NOP:
optlen = 1;
break;
default:
type = *(p++);
optlen = *(p++) - 2;
len -= 2;
if (type != __type)
break;
if (__optlen)
*__optlen = optlen;
if (__value)
*__value = p;
switch (optlen) {
case 0:
return 0;
case 1:
return *p;
case 2:
return ntohs(*(uint16_t *)p);
default:
return ntohl(*(uint32_t *)p);
}
}
}
return -1;
}
/**
* tcp_hash_match() - Check if a connection entry matches address and ports
* @conn: Connection entry to match against
* @af: Address family, AF_INET or AF_INET6
* @addr: Remote address, pointer to sin_addr or sin6_addr
* @tap_port: tap-facing port
* @sock_port: Socket-facing port
*
* Return: 1 on match, 0 otherwise
*/
static int tcp_hash_match(struct tcp_tap_conn *conn, int af, void *addr,
in_port_t tap_port, in_port_t sock_port)
{
if (af == AF_INET && IN6_IS_ADDR_V4MAPPED(&conn->a.a6) &&
!memcmp(&conn->a.a4.a, addr, sizeof(conn->a.a4.a)) &&
conn->tap_port == tap_port && conn->sock_port == sock_port)
return 1;
if (af == AF_INET6 &&
!memcmp(&conn->a.a6, addr, sizeof(conn->a.a6)) &&
conn->tap_port == tap_port && conn->sock_port == sock_port)
return 1;
return 0;
}
/**
* tcp_hash() - Calculate hash value for connection given address and ports
* @c: Execution context
* @af: Address family, AF_INET or AF_INET6
* @addr: Remote address, pointer to sin_addr or sin6_addr
* @tap_port: tap-facing port
* @sock_port: Socket-facing port
*
* Return: hash value, already modulo size of the hash table
*/
static unsigned int tcp_hash(struct ctx *c, int af, void *addr,
in_port_t tap_port, in_port_t sock_port)
{
uint64_t b = 0;
if (af == AF_INET) {
struct {
struct in_addr addr;
in_port_t tap_port;
in_port_t sock_port;
} __attribute__((__packed__)) in = {
.addr = *(struct in_addr *)addr,
.tap_port = tap_port,
.sock_port = sock_port,
};
b = siphash_8b((uint8_t *)&in, c->tcp.hash_secret);
} else if (af == AF_INET6) {
struct {
struct in6_addr addr;
in_port_t tap_port;
in_port_t sock_port;
} __attribute__((__packed__)) in = {
.addr = *(struct in6_addr *)addr,
.tap_port = tap_port,
.sock_port = sock_port,
};
b = siphash_20b((uint8_t *)&in, c->tcp.hash_secret);
}
return (unsigned int)(b % TCP_HASH_TABLE_SIZE);
}
/**
* tcp_hash_insert() - Insert connection into hash table, chain link
* @c: Execution context
* @conn: Connection pointer
* @af: Address family, AF_INET or AF_INET6
* @addr: Remote address, pointer to sin_addr or sin6_addr
*/
static void tcp_hash_insert(struct ctx *c, struct tcp_tap_conn *conn,
int af, void *addr)
{
int b;
b = tcp_hash(c, af, addr, conn->tap_port, conn->sock_port);
conn->next = tt_hash[b];
tt_hash[b] = conn;
conn->hash_bucket = b;
debug("TCP: hash table insert: index %i, sock %i, bucket: %i, next: %p",
conn - tt, conn->sock, b, conn->next);
}
/**
* tcp_hash_remove() - Drop connection from hash table, chain unlink
* @conn: Connection pointer
*/
static void tcp_hash_remove(struct tcp_tap_conn *conn)
{
struct tcp_tap_conn *entry, *prev = NULL;
int b = conn->hash_bucket;
for (entry = tt_hash[b]; entry; prev = entry, entry = entry->next) {
if (entry == conn) {
if (prev)
prev->next = conn->next;
else
tt_hash[b] = conn->next;
break;
}
}
debug("TCP: hash table remove: index %i, sock %i, bucket: %i, new: %p",
conn - tt, conn->sock, b, prev ? prev->next : tt_hash[b]);
}
/**
* tcp_hash_update() - Update pointer for given connection
* @old: Old connection pointer
* @new: New connection pointer
*/
static void tcp_hash_update(struct tcp_tap_conn *old, struct tcp_tap_conn *new)
{
struct tcp_tap_conn *entry, *prev = NULL;
int b = old->hash_bucket;
for (entry = tt_hash[b]; entry; prev = entry, entry = entry->next) {
if (entry == old) {
if (prev)
prev->next = new;
else
tt_hash[b] = new;
break;
}
}
debug("TCP: hash table update: old index %i, new index %i, sock %i, "
"bucket: %i, old: %p, new: %p",
old - tt, new - tt, new->sock, b, old, new);
}
/**
* tcp_hash_lookup() - Look up connection given remote address and ports
* @c: Execution context
* @af: Address family, AF_INET or AF_INET6
* @addr: Remote address, pointer to sin_addr or sin6_addr
* @tap_port: tap-facing port
* @sock_port: Socket-facing port
*
* Return: connection pointer, if found, -ENOENT otherwise
*/
static struct tcp_tap_conn *tcp_hash_lookup(struct ctx *c, int af, void *addr,
in_port_t tap_port,
in_port_t sock_port)
{
int b = tcp_hash(c, af, addr, tap_port, sock_port);
struct tcp_tap_conn *conn;
for (conn = tt_hash[b]; conn; conn = conn->next) {
if (tcp_hash_match(conn, af, addr, tap_port, sock_port))
return conn;
}
return NULL;
}
/**
* tcp_table_tap_compact - Compaction tap connection table
* @c: Execution context
* @hole: Pointer to recently closed connection
*/
static void tcp_table_tap_compact(struct ctx *c, struct tcp_tap_conn *hole)
{
union epoll_ref ref = { .proto = IPPROTO_TCP, .tcp.index = hole - tt };
struct tcp_tap_conn *from, *to;
struct epoll_event ev;
if ((hole - tt) == --c->tcp.tap_conn_count) {
bitmap_clear(tcp_act, hole - tt);
debug("TCP: hash table compaction: index %i (%p) was max index",
hole - tt, hole);
return;
}
from = &tt[c->tcp.tap_conn_count];
memcpy(hole, from, sizeof(*hole));
from->state = CLOSED;
to = hole;
tcp_hash_update(from, to);
if (to->state == SOCK_SYN_SENT)
ev.events = EPOLLRDHUP;
else if (to->state == TAP_SYN_SENT)
ev.events = EPOLLOUT | EPOLLRDHUP;
else
ev.events = EPOLLIN | EPOLLRDHUP;
ref.tcp.v6 = !IN6_IS_ADDR_V4MAPPED(&to->a.a6);
ref.s = from->sock;
ev.data.u64 = ref.u64;
epoll_ctl(c->epollfd, EPOLL_CTL_MOD, from->sock, &ev);
debug("TCP: hash table compaction: old index %i, new index %i, "
"sock %i, from: %p, to: %p",
from - tt, to - tt, from->sock, from, to);
}
/**
* tcp_tap_destroy() - Close tap connection, drop from hash table and epoll
* @c: Execution context
* @conn: Connection pointer
*/
static void tcp_tap_destroy(struct ctx *c, struct tcp_tap_conn *conn)
{
if (conn->state == CLOSED)
return;
epoll_ctl(c->epollfd, EPOLL_CTL_DEL, conn->sock, NULL);
tcp_tap_state(conn, CLOSED);
close(conn->sock);
tcp_hash_remove(conn);
tcp_table_tap_compact(c, conn);
}
static void tcp_rst(struct ctx *c, struct tcp_tap_conn *conn);
/**
* tcp_send_to_tap() - Send segment to tap, with options and values from socket
* @c: Execution context
* @conn: Connection pointer
* @flags: TCP flags to set
* @in: Payload buffer
* @len: Payload length
*
* Return: negative error code on connection reset, 0 otherwise
*/
static int tcp_send_to_tap(struct ctx *c, struct tcp_tap_conn *conn,
int flags, char *in, int len)
{
uint32_t ack_offset = conn->seq_from_tap - conn->seq_ack_to_tap;
char buf[USHRT_MAX] = { 0 }, *data;
struct tcp_info info = { 0 };
int ws = 0, err, ack_pending;
socklen_t sl = sizeof(info);
struct tcphdr *th;
if (!ack_offset && !flags) {
err = 0;
info.tcpi_bytes_acked = conn->tcpi_acked_last;
info.tcpi_snd_wnd = conn->tcpi_snd_wnd;
info.tcpi_snd_wscale = conn->ws;
} else if (conn->no_snd_wnd && !(flags & SYN)) {
err = 0;
} else {
err = getsockopt(conn->sock, SOL_TCP, TCP_INFO, &info, &sl);
if (err && !(flags & RST)) {
tcp_rst(c, conn);
return err;
}
conn->tcpi_snd_wnd = info.tcpi_snd_wnd;
}
th = (struct tcphdr *)buf;
data = (char *)(th + 1);
th->doff = sizeof(*th) / 4;
if ((flags & SYN) && !err) {
/* Options: MSS, NOP and window scale if allowed (4-8 bytes) */
*data++ = OPT_MSS;
*data++ = OPT_MSS_LEN;
*(uint16_t *)data = htons(info.tcpi_snd_mss);
data += OPT_MSS_LEN - 2;
th->doff += OPT_MSS_LEN / 4;
/* Check if kernel includes commit:
* 8f7baad7f035 ("tcp: Add snd_wnd to TCP_INFO")
*/
conn->no_snd_wnd = !info.tcpi_snd_wnd;
if (conn->ws_allowed && (ws = info.tcpi_snd_wscale) &&
!conn->no_snd_wnd) {
*data++ = OPT_NOP;
*data++ = OPT_WS;
*data++ = OPT_WS_LEN;
*data++ = ws;
th->doff += (1 + OPT_WS_LEN) / 4;
}
/* RFC 793, 3.1: "[...] and the first data octet is ISN+1." */
th->seq = htonl(conn->seq_to_tap++);
} else {
th->seq = htonl(conn->seq_to_tap);
conn->seq_to_tap += len;
}
if (flags & SYN) {
ack_pending = 0;
} else if (conn->no_snd_wnd) {
ack_pending = (conn->seq_from_tap - conn->seq_ack_to_tap) <
MAX_WINDOW;
} else {
ack_pending = info.tcpi_bytes_acked > conn->tcpi_acked_last;
}
if (!err && (ack_pending || (flags & ACK) || len)) {
th->ack = 1;
if (conn->no_snd_wnd) {
conn->seq_ack_to_tap = conn->seq_from_tap;
} else {
conn->seq_ack_to_tap = info.tcpi_bytes_acked +
conn->seq_init_from_tap;
conn->tcpi_acked_last = info.tcpi_bytes_acked;
}
if (conn->state == LAST_ACK ||
conn->state == FIN_WAIT_1_SOCK_FIN)
conn->seq_ack_to_tap = conn->seq_from_tap + 1;
if (conn->state == LAST_ACK)
th->seq = htonl(ntohl(th->seq) + 1);
th->ack_seq = htonl(conn->seq_ack_to_tap);
} else {
if (!len && !flags)
return 0;
th->ack = th->ack_seq = 0;
}
th->rst = !!(flags & RST);
th->syn = !!(flags & SYN);
th->fin = !!(flags & FIN);
th->source = htons(conn->sock_port);
th->dest = htons(conn->tap_port);
if (flags & ZERO_WINDOW) {
th->window = 0;
} else if (!err && !conn->no_snd_wnd) {
/* First value sent by receiver is not scaled */
th->window = htons(info.tcpi_snd_wnd >>
(th->syn ? 0 : info.tcpi_snd_wscale));
} else {
th->window = htons(WINDOW_DEFAULT);
}
th->urg_ptr = 0;
th->check = 0;
memcpy(data, in, len);
tap_ip_send(c, &conn->a.a6, IPPROTO_TCP, buf, th->doff * 4 + len,
conn->seq_init_to_tap);
return 0;
}
/**
* tcp_rst() - Reset a tap connection: send RST segment to tap, close socket
* @c: Execution context
* @conn: Connection pointer
*/
static void tcp_rst(struct ctx *c, struct tcp_tap_conn *conn)
{
if (conn->state == CLOSED)
return;
tcp_send_to_tap(c, conn, RST, NULL, 0);
tcp_tap_destroy(c, conn);
}
/**
* tcp_clamp_window() - Set window and scaling from option, clamp on socket
* @conn: Connection pointer
* @th: TCP header, from tap
* @len: Buffer length, at L4
* @init: Set if this is the very first segment from tap
*/
static void tcp_clamp_window(struct tcp_tap_conn *conn, struct tcphdr *th,
int len, int init)
{
if (init) {
conn->ws = tcp_opt_get(th, len, OPT_WS, NULL, NULL);
conn->ws_allowed = conn->ws >= 0 && conn->ws <= MAX_WS;
conn->ws *= conn->ws_allowed;
/* 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.
*/
conn->tap_window = ntohs(th->window);
conn->window_clamped = 0;
} else {
unsigned int window = ntohs(th->window) << conn->ws;
if (conn->window_clamped) {
if (conn->tap_window == window)
return;
/* Discard +/- 1% updates to spare some syscalls. */
if ((window > conn->tap_window &&
window * 99 / 100 < conn->tap_window) ||
(window < conn->tap_window &&
window * 101 / 100 > conn->tap_window)) {
conn->tap_window = window;
return;
}
}
conn->tap_window = window;
if (window < 256)
window = 256;
setsockopt(conn->sock, SOL_TCP, TCP_WINDOW_CLAMP,
&window, sizeof(window));
conn->window_clamped = 1;
}
}
/**
* tcp_seq_init() - Calculate initial sequence number according to RFC 6528
* @c: Execution context
* @af: Address family, AF_INET or AF_INET6
* @addr: Remote address, pointer to sin_addr or sin6_addr
* @dstport: Destination port, connection-wise, network order
* @srcport: Source port, connection-wise, network order
* @now: Current timestamp
*
* Return: initial TCP sequence
*/
static uint32_t tcp_seq_init(struct ctx *c, int af, void *addr,
in_port_t dstport, in_port_t srcport,
struct timespec *now)
{
uint32_t ns, seq = 0;
if (af == AF_INET) {
struct {
struct in_addr src;
in_port_t srcport;
struct in_addr dst;
in_port_t dstport;
} __attribute__((__packed__)) in = {
.src = *(struct in_addr *)addr,
.srcport = srcport,
.dst = { c->addr4 },
.dstport = dstport,
};
seq = siphash_12b((uint8_t *)&in, c->tcp.hash_secret);
} else if (af == AF_INET6) {
struct {
struct in6_addr src;
in_port_t srcport;
struct in6_addr dst;
in_port_t dstport;
} __attribute__((__packed__)) in = {
.src = *(struct in6_addr *)addr,
.srcport = srcport,
.dst = c->addr6,
.dstport = dstport,
};
seq = siphash_36b((uint8_t *)&in, c->tcp.hash_secret);
}
ns = now->tv_sec * 1E9;
ns += now->tv_nsec >> 5; /* 32ns ticks, overflows 32 bits every 137s */
return seq + ns;
}
/**
* tcp_conn_from_tap() - Handle connection request (SYN segment) from tap
* @c: Execution context
* @af: Address family, AF_INET or AF_INET6
* @addr: Remote address, pointer to sin_addr or sin6_addr
* @th: TCP header from tap
* @len: Packet length at L4
* @now: Current timestamp
*/
static void tcp_conn_from_tap(struct ctx *c, int af, void *addr,
struct tcphdr *th, size_t len,
struct timespec *now)
{
struct sockaddr_in addr4 = {
.sin_family = AF_INET,
.sin_port = th->dest,
.sin_addr = *(struct in_addr *)addr,
};
struct sockaddr_in6 addr6 = {
.sin6_family = AF_INET6,
.sin6_port = th->dest,
.sin6_addr = *(struct in6_addr *)addr,
};
struct epoll_event ev = { .events = EPOLLIN | EPOLLRDHUP };
union epoll_ref ref = { .proto = IPPROTO_TCP };
const struct sockaddr *sa;
struct tcp_tap_conn *conn;
socklen_t sl;
int s;
if (c->tcp.tap_conn_count >= MAX_TAP_CONNS)
return;
ref.s = s = socket(af, SOCK_STREAM | SOCK_NONBLOCK, IPPROTO_TCP);
if (s < 0)
return;
conn = &tt[c->tcp.tap_conn_count++];
conn->sock = s;
conn->mss_guest = tcp_opt_get(th, len, OPT_MSS, NULL, NULL);
if (conn->mss_guest < 0)
conn->mss_guest = MSS_DEFAULT;
if (c->mode == MODE_PASST) {
/* Don't upset qemu */
conn->mss_guest = MIN(USHRT_MAX -
sizeof(uint32_t) -
sizeof(struct ethhdr) -
sizeof(struct ipv6hdr) -
sizeof(struct tcphdr),
conn->mss_guest);
}
sl = sizeof(conn->mss_guest);
setsockopt(s, SOL_TCP, TCP_MAXSEG, &conn->mss_guest, sl);
tcp_clamp_window(conn, th, len, 1);
if (af == AF_INET) {
sa = (struct sockaddr *)&addr4;
sl = sizeof(addr4);
memset(&conn->a.a4.zero, 0, sizeof(conn->a.a4.zero));
memset(&conn->a.a4.one, 0xff, sizeof(conn->a.a4.one));
memcpy(&conn->a.a4.a, addr, sizeof(conn->a.a4.a));
} else {
sa = (struct sockaddr *)&addr6;
sl = sizeof(addr6);
memcpy(&conn->a.a6, addr, sizeof(conn->a.a6));
}
conn->sock_port = ntohs(th->dest);
conn->tap_port = ntohs(th->source);
conn->ts_sock = conn->ts_tap = conn->ts_ack_tap = *now;
bitmap_set(tcp_act, conn - tt);
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;
conn->seq_to_tap = tcp_seq_init(c, af, addr, th->dest, th->source, now);
conn->seq_init_to_tap = conn->seq_to_tap;
conn->seq_ack_from_tap = conn->seq_to_tap + 1;
tcp_hash_insert(c, conn, af, addr);
if (connect(s, sa, sl)) {
tcp_tap_state(conn, TAP_SYN_SENT);
if (errno != EINPROGRESS) {
tcp_rst(c, conn);
return;
}
ev.events = EPOLLOUT | EPOLLRDHUP;
} else {
tcp_tap_state(conn, TAP_SYN_RCVD);
if (tcp_send_to_tap(c, conn, SYN | ACK, NULL, 0))
return;
}
ref.tcp.index = conn - tt;
ev.data.u64 = ref.u64;
epoll_ctl(c->epollfd, EPOLL_CTL_ADD, s, &ev);
}
/**
* tcp_table_splice_compact - Compact spliced connection table
* @c: Execution context
* @hole: Pointer to recently closed connection
*/
static void tcp_table_splice_compact(struct ctx *c,
struct tcp_splice_conn *hole)
{
union epoll_ref ref_from = { .proto = IPPROTO_TCP,
.tcp.index = hole - ts };
union epoll_ref ref_to = { .proto = IPPROTO_TCP,
.tcp.index = hole - ts };
struct tcp_splice_conn *move;
struct epoll_event ev_from;
struct epoll_event ev_to;
if ((hole - ts) == --c->tcp.splice_conn_count)
return;
move = &ts[c->tcp.splice_conn_count];
memcpy(hole, move, sizeof(*hole));
move->state = CLOSED;
move = hole;
ref_from.s = move->from;
ref_from.tcp.v6 = move->v6;
ref_to.s = move->to;
ref_to.tcp.v6 = move->v6;
if (move->state == SPLICE_ACCEPTED) {
ev_from.events = ev_to.events = 0;
} else if (move->state == SPLICE_CONNECT) {
ev_from.events = EPOLLET | EPOLLRDHUP;
ev_to.events = EPOLLET | EPOLLOUT | EPOLLRDHUP;
} else {
ev_from.events = EPOLLET | EPOLLIN | EPOLLOUT | EPOLLRDHUP;
ev_to.events = EPOLLET | EPOLLIN | EPOLLOUT | EPOLLRDHUP;
}
ev_from.data.u64 = ref_from.u64;
ev_to.data.u64 = ref_to.u64;
epoll_ctl(c->epollfd, EPOLL_CTL_MOD, move->from, &ev_from);
epoll_ctl(c->epollfd, EPOLL_CTL_MOD, move->to, &ev_to);
}
/**
* tcp_tap_destroy() - Close spliced connection and pipes, drop from epoll
* @c: Execution context
* @conn: Connection pointer
*/
static void tcp_splice_destroy(struct ctx *c, struct tcp_splice_conn *conn)
{
switch (conn->state) {
case SPLICE_ESTABLISHED:
if (conn->pipe_from_to[0] != -1) {
close(conn->pipe_from_to[0]);
close(conn->pipe_from_to[1]);
}
if (conn->pipe_to_from[0] != -1) {
close(conn->pipe_to_from[0]);
close(conn->pipe_to_from[1]);
}
/* Falls through */
case SPLICE_CONNECT:
epoll_ctl(c->epollfd, EPOLL_CTL_DEL, conn->from, NULL);
epoll_ctl(c->epollfd, EPOLL_CTL_DEL, conn->to, NULL);
close(conn->to);
/* Falls through */
case SPLICE_ACCEPTED:
close(conn->from);
tcp_splice_state(conn, CLOSED);
tcp_table_splice_compact(c, conn);
return;
default:
return;
}
}
/**
* tcp_sock_consume() - Consume (discard) data from buffer, update ACK sequence
* @conn: Connection pointer
* @ack_seq: ACK sequence, host order
*/
static void tcp_sock_consume(struct tcp_tap_conn *conn, uint32_t ack_seq)
{
uint32_t to_ack;
/* Implicitly take care of wrap-arounds */
to_ack = ack_seq - conn->seq_ack_from_tap;
/* 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 (to_ack > MAX_WINDOW)
return;
if (to_ack)
recv(conn->sock, NULL, to_ack, MSG_DONTWAIT | MSG_TRUNC);
conn->seq_ack_from_tap = ack_seq;
}
/**
* tcp_data_from_sock() - Handle new data from socket, queue to tap, in window
* @c: Execution context
* @conn: Connection pointer
* @now: Current timestamp
*
* Return: negative on connection reset, 0 otherwise
*/
static int tcp_data_from_sock(struct ctx *c, struct tcp_tap_conn *conn,
struct timespec *now)
{
int *buf_mss, *buf_mss_nr_set, *buf_mss_tap, *buf_mss_tap_nr_set;
int mss_tap, fill_bufs, send_bufs = 0, last_len, iov_rem = 0;
int send, len, plen, v4 = IN6_IS_ADDR_V4MAPPED(&conn->a.a6);
uint32_t seq_to_tap = conn->seq_to_tap;
socklen_t sl = sizeof(struct tcp_info);
int s = conn->sock, i, ret = 0;
struct iovec *iov, *iov_tap;
uint32_t already_sent;
struct tcp_info info;
struct mmsghdr *mh;
already_sent = conn->seq_to_tap - conn->seq_ack_from_tap;
if (!conn->tap_window || already_sent >= conn->tap_window)
return 0;
fill_bufs = DIV_ROUND_UP(conn->tap_window - already_sent,
conn->mss_guest);
if (fill_bufs > TCP_TAP_FRAMES) {
fill_bufs = TCP_TAP_FRAMES;
iov_rem = 0;
} else {
iov_rem = (conn->tap_window - already_sent) % conn->mss_guest;
}
/* Adjust iovec length for recvmsg() based on what was set last time. */
if (v4) {
iov = tcp4_l2_iov_sock + 1;
buf_mss = &tcp4_l2_buf_mss;
buf_mss_nr_set = &tcp4_l2_buf_mss_nr_set;
} else {
iov = tcp6_l2_iov_sock + 1;
buf_mss = &tcp6_l2_buf_mss;
buf_mss_nr_set = &tcp6_l2_buf_mss_nr_set;
}
if (*buf_mss != conn->mss_guest)
*buf_mss_nr_set = 0;
for (i = *buf_mss_nr_set; i < fill_bufs; i++)
iov[i].iov_len = conn->mss_guest;
*buf_mss = conn->mss_guest;
*buf_mss_nr_set = fill_bufs - 1;
/* First buffer is to discard data, last one may be partially filled. */
iov[-1].iov_len = already_sent;
if (iov_rem)
iov[fill_bufs - 1].iov_len = iov_rem;
if (v4)
tcp4_l2_mh_sock.msg_iovlen = fill_bufs + 1;
else
tcp6_l2_mh_sock.msg_iovlen = fill_bufs + 1;
/* Don't dequeue until acknowledged by guest. */
len = recvmsg(s, v4 ? &tcp4_l2_mh_sock : &tcp6_l2_mh_sock, MSG_PEEK);
if (len < 0)
goto err;
if (!len)
goto zero_len;
send = len - already_sent;
if (send <= 0)
goto out_restore_iov;
send_bufs = DIV_ROUND_UP(send, conn->mss_guest);
last_len = send - (send_bufs - 1) * conn->mss_guest;
/* Adjust iovec length for sending based on what was set last time. */
if (v4) {
mss_tap = conn->mss_guest +
offsetof(struct tcp4_l2_buf_t, data) -
offsetof(struct tcp4_l2_buf_t, vnet_len);
iov_tap = tcp4_l2_iov_tap;
buf_mss_tap = &tcp4_l2_buf_mss_tap;
buf_mss_tap_nr_set = &tcp4_l2_buf_mss_tap_nr_set;
} else {
mss_tap = conn->mss_guest +
offsetof(struct tcp6_l2_buf_t, data) -
offsetof(struct tcp6_l2_buf_t, vnet_len);
iov_tap = tcp6_l2_iov_tap;
buf_mss_tap = &tcp6_l2_buf_mss_tap;
buf_mss_tap_nr_set = &tcp6_l2_buf_mss_tap_nr_set;
}
if (*buf_mss_tap != mss_tap)
*buf_mss_tap_nr_set = 0;
for (i = *buf_mss_tap_nr_set; i < send_bufs; i++)
iov_tap[i].iov_len = mss_tap;
*buf_mss_tap = mss_tap;
*buf_mss_tap_nr_set = send_bufs;
iov_tap[send_bufs - 1].iov_len = mss_tap - conn->mss_guest + last_len;
/* Likely, some new data was acked too. */
if (conn->seq_from_tap != conn->seq_ack_to_tap) {
if (conn->no_snd_wnd) {
conn->seq_ack_to_tap = conn->seq_from_tap;
} else {
if (getsockopt(conn->sock, SOL_TCP, TCP_INFO, &info,
&sl))
goto err;
conn->tcpi_acked_last = info.tcpi_bytes_acked;
conn->seq_ack_to_tap = info.tcpi_bytes_acked +
conn->seq_init_from_tap;
}
} else {
info.tcpi_snd_wscale = conn->ws;
info.tcpi_snd_wnd = conn->tcpi_snd_wnd;
}
plen = conn->mss_guest;
for (i = 0, mh = tcp_l2_mh_tap; i < send_bufs; i++, mh++) {
int ip_len;
if (i == send_bufs - 1)
plen = last_len;
if (v4) {
struct tcp4_l2_buf_t *b = &tcp4_l2_buf[i];
ip_len = plen + sizeof(struct iphdr) +
sizeof(struct tcphdr);
b->iph.tot_len = htons(ip_len);
b->iph.saddr = conn->a.a4.a.s_addr;
b->iph.daddr = c->addr4_seen;
if (!i || i == send_bufs - 1)
tcp_update_check_ip4(b);
else
b->iph.check = tcp4_l2_buf[0].iph.check;
b->th.source = htons(conn->sock_port);
b->th.dest = htons(conn->tap_port);
b->th.seq = htonl(seq_to_tap);
b->th.ack_seq = htonl(conn->seq_ack_to_tap);
if (conn->no_snd_wnd) {
b->th.window = htons(WINDOW_DEFAULT);
} else {
b->th.window = htons(info.tcpi_snd_wnd >>
info.tcpi_snd_wscale);
conn->tcpi_snd_wnd = info.tcpi_snd_wnd;
}
tcp_update_check_tcp4(b);
if (c->mode == MODE_PASTA) {
ip_len += sizeof(struct ethhdr);
write(c->fd_tap, &b->eh, ip_len);
pcap((char *)&b->eh, ip_len);
conn->seq_to_tap += plen;
continue;
}
b->vnet_len = htonl(sizeof(struct ethhdr) + ip_len);
mh->msg_hdr.msg_iov = &tcp4_l2_iov_tap[i];
} else {
struct tcp6_l2_buf_t *b = &tcp6_l2_buf[i];
uint32_t flow = conn->seq_init_to_tap;
ip_len = plen + sizeof(struct ipv6hdr) +
sizeof(struct tcphdr);
b->ip6h.payload_len = htons(plen +
sizeof(struct tcphdr));
b->ip6h.saddr = conn->a.a6;
if (IN6_IS_ADDR_LINKLOCAL(&b->ip6h.saddr))
b->ip6h.daddr = c->addr6_ll_seen;
else
b->ip6h.daddr = c->addr6_seen;
b->th.source = htons(conn->sock_port);
b->th.dest = htons(conn->tap_port);
b->th.seq = htonl(seq_to_tap);
b->th.ack_seq = htonl(conn->seq_ack_to_tap);
if (conn->no_snd_wnd) {
b->th.window = htons(WINDOW_DEFAULT);
} else {
b->th.window = htons(info.tcpi_snd_wnd >>
info.tcpi_snd_wscale);
conn->tcpi_snd_wnd = info.tcpi_snd_wnd;
}
memset(b->ip6h.flow_lbl, 0, 3);
tcp_update_check_tcp6(b);
b->ip6h.flow_lbl[0] = (flow >> 16) & 0xf;
b->ip6h.flow_lbl[1] = (flow >> 8) & 0xff;
b->ip6h.flow_lbl[2] = (flow >> 0) & 0xff;
if (c->mode == MODE_PASTA) {
ip_len += sizeof(struct ethhdr);
write(c->fd_tap, &b->eh, ip_len);
pcap((char *)&b->eh, ip_len);
conn->seq_to_tap += plen;
continue;
}
b->vnet_len = htonl(sizeof(struct ethhdr) + ip_len);
mh->msg_hdr.msg_iov = &tcp6_l2_iov_tap[i];
}
seq_to_tap += plen;
}
if (c->mode == MODE_PASTA)
goto out;
ret = sendmmsg(c->fd_tap, tcp_l2_mh_tap, mh - tcp_l2_mh_tap,
MSG_NOSIGNAL | MSG_DONTWAIT);
if (ret <= 0)
goto out;
conn->seq_to_tap += conn->mss_guest * (ret - 1) + last_len;
/* sendmmsg() indicates how many messages were sent at least partially.
* Kernel commit 3023898b7d4a ("sock: fix sendmmsg for partial sendmsg")
* gives us the guarantee that at most one message, namely the last sent
* one, might have been sent partially. Check how many bytes of that
* message were sent, and re-send any missing bytes with a blocking
* sendmsg(), otherwise qemu will fail to parse any subsequent message.
*/
mh = &tcp_l2_mh_tap[ret - 1];
if (mh->msg_len < mh->msg_hdr.msg_iov->iov_len) {
uint8_t **iov_base = (uint8_t **)&mh->msg_hdr.msg_iov->iov_base;
int part_sent = mh->msg_len;
mh->msg_hdr.msg_iov->iov_len -= part_sent;
*iov_base += part_sent;
sendmsg(c->fd_tap, &mh->msg_hdr, MSG_NOSIGNAL);
mh->msg_hdr.msg_iov->iov_len += part_sent;
*iov_base -= part_sent;
}
pcapmm(tcp_l2_mh_tap, ret);
goto out;
err:
if (errno != EAGAIN && errno != EWOULDBLOCK) {
tcp_rst(c, conn);
ret = -errno;
}
goto out_restore_iov;
zero_len:
if (conn->state == FIN_WAIT_1) {
tcp_tap_state(conn, FIN_WAIT_1_SOCK_FIN);
} else if (conn->state < ESTABLISHED_SOCK_FIN) {
tcp_tap_state(conn, ESTABLISHED_SOCK_FIN);
shutdown(conn->sock, SHUT_RD);
tcp_send_to_tap(c, conn, FIN | ACK, NULL, 0);
}
goto out_restore_iov;
out:
conn->ts_sock = *now;
out_restore_iov:
if (iov_rem)
iov[fill_bufs - 1].iov_len = conn->mss_guest;
if (send_bufs)
iov_tap[send_bufs - 1].iov_len = mss_tap;
return ret;
}
/**
* tcp_data_from_tap() - tap data in ESTABLISHED{,SOCK_FIN}, CLOSE_WAIT states
* @c: Execution context
* @conn: Connection pointer
* @msg: Array of messages from tap
* @count: Count of messages
* @now: Current timestamp
*/
static void tcp_data_from_tap(struct ctx *c, struct tcp_tap_conn *conn,
struct tap_msg *msg, int count,
struct timespec *now)
{
int i, iov_i, keep = -1, ack = 0, fin = 0, retr = 0;
struct msghdr mh = { .msg_iov = tcp_tap_iov };
uint32_t max_ack_seq = conn->seq_ack_from_tap;
uint32_t seq_from_tap = conn->seq_from_tap;
uint16_t max_ack_seq_wnd;
ssize_t len;
for (i = 0, iov_i = 0; i < count; i++) {
struct tcphdr *th = (struct tcphdr *)msg[i].l4h;
uint32_t seq, seq_offset, ack_seq;
size_t len = msg[i].l4_len, off;
char *data;
if (len < sizeof(*th)) {
tcp_rst(c, conn);
return;
}
off = th->doff * 4;
if (off < sizeof(*th) || off > len) {
tcp_rst(c, conn);
return;
}
if (th->rst) {
tcp_tap_destroy(c, conn);
return;
}
len -= off;
data = (char *)th + off;
seq = ntohl(th->seq);
ack_seq = ntohl(th->ack_seq);
if (!i) {
if (count == 1)
max_ack_seq_wnd = ntohs(th->window);
else
max_ack_seq_wnd = ntohs(th->window) - 1;
}
if (th->ack) {
ack = 1;
if (ack_seq - conn->seq_ack_from_tap < MAX_WINDOW &&
ack_seq - max_ack_seq < MAX_WINDOW) {
/* Fast re-transmit */
retr = !len && ack_seq == max_ack_seq &&
max_ack_seq_wnd == ntohs(th->window);
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 i.e. > MAX_WINDOW)
*/
if (seq_offset < MAX_WINDOW && seq + len <= seq_from_tap)
continue;
if (seq_offset > MAX_WINDOW) {
if (keep != -1)
keep = i;
continue;
}
tcp_tap_iov[iov_i].iov_base = data + seq_offset;
tcp_tap_iov[iov_i].iov_len = len - seq_offset;
seq_from_tap += tcp_tap_iov[iov_i].iov_len;
iov_i++;
if (keep == i) {
i = keep + 1;
keep = -1;
}
}
if (ack) {
conn->ts_ack_tap = *now;
tcp_sock_consume(conn, max_ack_seq);
}
if (retr) {
conn->seq_to_tap = max_ack_seq;
tcp_data_from_sock(c, conn, now);
}
if (!iov_i) {
if (keep != -1) {
tcp_send_to_tap(c, conn, ACK, NULL, 0);
tcp_send_to_tap(c, conn, ACK, NULL, 0);
}
goto fin;
}
mh.msg_iovlen = iov_i;
len = sendmsg(conn->sock, &mh, MSG_DONTWAIT | MSG_NOSIGNAL);
if (len < 0) {
if (errno == EAGAIN || errno == EWOULDBLOCK) {
tcp_send_to_tap(c, conn, ZERO_WINDOW, NULL, 0);
return;
}
tcp_rst(c, conn);
return;
}
if (len < (seq_from_tap - conn->seq_from_tap)) {
conn->seq_from_tap += len;
tcp_send_to_tap(c, conn, ZERO_WINDOW, NULL, 0);
return;
}
conn->seq_from_tap += len;
if (!fin)
tcp_send_to_tap(c, conn, 0, NULL, 0);
fin:
if (conn->state == ESTABLISHED_SOCK_FIN && ack &&
!tcp_data_from_sock(c, conn, now))
tcp_tap_state(conn, CLOSE_WAIT);
if (fin) {
shutdown(conn->sock, SHUT_WR);
if (conn->state == ESTABLISHED) {
tcp_tap_state(conn, FIN_WAIT_1);
tcp_data_from_sock(c, conn, now);
} else {
tcp_tap_state(conn, LAST_ACK);
}
}
}
/**
* tcp_tap_handler() - Handle packets from tap and state transitions
* @c: Execution context
* @af: Address family, AF_INET or AF_INET6
* @addr: Destination address
* @msg: Input messages
* @count: Message count
* @now: Current timestamp
*
* Return: count of consumed packets
*/
int tcp_tap_handler(struct ctx *c, int af, void *addr,
struct tap_msg *msg, int count, struct timespec *now)
{
union epoll_ref ref = { .proto = IPPROTO_TCP,
.tcp.v6 = ( af == AF_INET6 ) };
struct tcphdr *th = (struct tcphdr *)msg[0].l4h;
size_t len = msg[0].l4_len, off;
struct tcp_tap_conn *conn;
struct epoll_event ev;
int ws;
if (len < sizeof(*th))
return 1;
off = th->doff * 4;
if (off < sizeof(*th) || off > len)
return 1;
conn = tcp_hash_lookup(c, af, addr, htons(th->source), htons(th->dest));
if (!conn) {
if (th->syn && !th->ack)
tcp_conn_from_tap(c, af, addr, th, len, now);
return 1;
}
if (th->rst) {
tcp_tap_destroy(c, conn);
return 1;
}
tcp_clamp_window(conn, th, len, th->syn && th->ack);
conn->ts_tap = *now;
switch (conn->state) {
case SOCK_SYN_SENT:
if (!th->syn || !th->ack) {
tcp_rst(c, conn);
return 1;
}
conn->mss_guest = tcp_opt_get(th, len, OPT_MSS, NULL, NULL);
if (conn->mss_guest < 0)
conn->mss_guest = MSS_DEFAULT;
if (c->mode == MODE_PASST) {
/* Don't upset qemu */
conn->mss_guest = MIN(USHRT_MAX -
sizeof(uint32_t) -
sizeof(struct ethhdr) -
sizeof(struct ipv6hdr) -
sizeof(struct tcphdr),
conn->mss_guest);
}
ws = tcp_opt_get(th, len, OPT_WS, NULL, NULL);
if (ws > MAX_WS) {
if (tcp_send_to_tap(c, conn, RST, NULL, 0))
return 1;
conn->seq_to_tap = 0;
conn->ws_allowed = 0;
tcp_send_to_tap(c, conn, SYN, NULL, 0);
return 1;
}
/* info.tcpi_bytes_acked already includes one byte for SYN, but
* not for incoming connections.
*/
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;
tcp_tap_state(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, now);
tcp_send_to_tap(c, conn, 0, NULL, 0);
ev.events = EPOLLIN | EPOLLRDHUP;
ref.s = conn->sock;
ref.tcp.index = conn - tt;
ev.data.u64 = ref.u64;
epoll_ctl(c->epollfd, EPOLL_CTL_MOD, conn->sock, &ev);
break;
case TAP_SYN_RCVD:
if (th->fin) {
shutdown(conn->sock, SHUT_WR);
tcp_tap_state(conn, FIN_WAIT_1);
break;
}
if (!th->ack) {
tcp_rst(c, conn);
return 1;
}
tcp_tap_state(conn, ESTABLISHED);
break;
case ESTABLISHED:
case ESTABLISHED_SOCK_FIN:
case CLOSE_WAIT:
tcp_data_from_tap(c, conn, msg, count, now);
return count;
case FIN_WAIT_1:
tcp_send_to_tap(c, conn, ACK, NULL, 0);
break;
case FIN_WAIT_1_SOCK_FIN:
if (th->ack)
tcp_tap_destroy(c, conn);
break;
case TAP_SYN_SENT:
case LAST_ACK:
case SPLICE_ACCEPTED:
case SPLICE_CONNECT:
case SPLICE_ESTABLISHED:
case CLOSED: /* ;) */
break;
}
return 1;
}
/**
* tcp_connect_finish() - Handle completion of connect() from EPOLLOUT event
* @c: Execution context
* @s: File descriptor number for socket
* @ref: epoll reference
*/
static void tcp_connect_finish(struct ctx *c, struct tcp_tap_conn *conn,
union epoll_ref ref)
{
struct epoll_event ev;
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_to_tap(c, conn, SYN | ACK, NULL, 0))
return;
/* Drop EPOLLOUT, only used to wait for connect() to complete */
ev.events = EPOLLIN | EPOLLRDHUP;
ev.data.u64 = ref.u64;
epoll_ctl(c->epollfd, EPOLL_CTL_MOD, conn->sock, &ev);
tcp_tap_state(conn, TAP_SYN_RCVD);
}
/**
* tcp_splice_connect_finish() - Completion of connect() or call on success
* @c: Execution context
* @conn: Connection pointer
* @v6: Set on IPv6 connection
*/
static void tcp_splice_connect_finish(struct ctx *c,
struct tcp_splice_conn *conn, int v6)
{
union epoll_ref ref_from = { .proto = IPPROTO_TCP, .s = conn->from,
.tcp = { .splice = 1, .v6 = v6,
.index = conn - ts } };
union epoll_ref ref_to = { .proto = IPPROTO_TCP, .s = conn->to,
.tcp = { .splice = 1, .v6 = v6,
.index = conn - ts } };
struct epoll_event ev_from, ev_to;
if (conn->state == SPLICE_CONNECT) {
socklen_t sl;
int so;
sl = sizeof(so);
if (getsockopt(conn->to, SOL_SOCKET, SO_ERROR, &so, &sl) ||
so) {
tcp_splice_destroy(c, conn);
return;
}
tcp_splice_state(conn, SPLICE_ESTABLISHED);
ev_from.events = ev_to.events = EPOLLIN | EPOLLET | EPOLLRDHUP;
ev_from.data.u64 = ref_from.u64;
ev_to.data.u64 = ref_to.u64;
epoll_ctl(c->epollfd, EPOLL_CTL_MOD, conn->from, &ev_from);
epoll_ctl(c->epollfd, EPOLL_CTL_MOD, conn->to, &ev_to);
}
conn->pipe_from_to[0] = conn->pipe_to_from[0] = -1;
if (pipe2(conn->pipe_to_from, O_NONBLOCK) ||
pipe2(conn->pipe_from_to, O_NONBLOCK)) {
tcp_splice_destroy(c, conn);
return;
}
fcntl(conn->pipe_from_to[0], F_SETPIPE_SZ, PIPE_SIZE);
fcntl(conn->pipe_to_from[0], F_SETPIPE_SZ, PIPE_SIZE);
}
/**
* tcp_splice_connect() - Create and connect socket for new spliced connection
* @c: Execution context
* @conn: Connection pointer
* @v6: Set on IPv6 connection
* @port: Destination port, host order
*
* Return: 0 for connect() succeeded or in progress, negative value on error
*/
static int tcp_splice_connect(struct ctx *c, struct tcp_splice_conn *conn,
int v6, in_port_t port)
{
int sock_conn = socket(v6 ? AF_INET6 : AF_INET,
SOCK_STREAM | SOCK_NONBLOCK, IPPROTO_TCP);
union epoll_ref ref_accept = { .proto = IPPROTO_TCP, .s = conn->from,
.tcp = { .splice = 1, .v6 = v6,
.index = conn - ts } };
union epoll_ref ref_conn = { .proto = IPPROTO_TCP, .s = sock_conn,
.tcp = { .splice = 1, .v6 = v6,
.index = conn - ts } };
struct epoll_event ev_accept = { .events = EPOLLRDHUP | EPOLLET,
.data.u64 = ref_accept.u64 };
struct epoll_event ev_conn = { .events = EPOLLRDHUP | EPOLLET,
.data.u64 = ref_conn.u64 };
struct sockaddr_in6 addr6 = {
.sin6_family = AF_INET6,
.sin6_port = htons(port),
.sin6_addr = IN6ADDR_LOOPBACK_INIT,
};
struct sockaddr_in addr4 = {
.sin_family = AF_INET,
.sin_port = htons(port),
.sin_addr = { .s_addr = htonl(INADDR_LOOPBACK) },
};
const struct sockaddr *sa;
int ret, one = 1;
socklen_t sl;
if (sock_conn < 0)
return -errno;
conn->to = sock_conn;
setsockopt(conn->from, SOL_TCP, TCP_CORK, &one, sizeof(one));
setsockopt(conn->from, SOL_TCP, TCP_NODELAY, &one, sizeof(one));
setsockopt(conn->to, SOL_TCP, TCP_CORK, &one, sizeof(one));
setsockopt(conn->to, SOL_TCP, TCP_NODELAY, &one, sizeof(one));
if (v6) {
sa = (struct sockaddr *)&addr6;
sl = sizeof(addr6);
} else {
sa = (struct sockaddr *)&addr4;
sl = sizeof(addr4);
}
if (connect(conn->to, sa, sl)) {
if (errno != EINPROGRESS) {
ret = -errno;
close(sock_conn);
return ret;
}
tcp_splice_state(conn, SPLICE_CONNECT);
ev_conn.events |= EPOLLOUT;
} else {
tcp_splice_state(conn, SPLICE_ESTABLISHED);
tcp_splice_connect_finish(c, conn, v6);
ev_conn.events |= EPOLLIN;
ev_accept.events |= EPOLLIN;
}
epoll_ctl(c->epollfd, EPOLL_CTL_ADD, conn->from, &ev_accept);
epoll_ctl(c->epollfd, EPOLL_CTL_ADD, conn->to, &ev_conn);
return 0;
}
/**
* struct tcp_splice_connect_ns_arg - Arguments for tcp_splice_connect_ns()
* @c: Execution context
* @conn: Accepted inbound connection
* @v6: Set for inbound IPv6 connection
* @port: Destination port, host order
* @ret: Return value of tcp_splice_connect_ns()
*/
struct tcp_splice_connect_ns_arg {
struct ctx *c;
struct tcp_splice_conn *conn;
int v6;
in_port_t port;
int ret;
};
/**
* tcp_splice_connect_ns() - Enter namespace and call tcp_splice_connect()
* @arg: See struct tcp_splice_connect_ns_arg
*
* Return: 0
*/
static int tcp_splice_connect_ns(void *arg)
{
struct tcp_splice_connect_ns_arg *a;
a = (struct tcp_splice_connect_ns_arg *)arg;
ns_enter(a->c->pasta_pid);
a->ret = tcp_splice_connect(a->c, a->conn, a->v6, a->port);
return 0;
}
/**
* tcp_splice_new() - Handle new inbound, spliced connection
* @c: Execution context
* @conn: Connection pointer
* @v6: Set for IPv6 connection
* @port: Destination port, host order
*
* Return: return code from connect()
*/
static int tcp_splice_new(struct ctx *c, struct tcp_splice_conn *conn,
int v6, in_port_t port)
{
struct tcp_splice_connect_ns_arg ns_arg = { c, conn, v6, port, 0 };
char ns_fn_stack[NS_FN_STACK_SIZE];
if ((!v6 && bitmap_isset(c->tcp.port4_to_ns, port)) ||
(v6 && bitmap_isset(c->tcp.port6_to_ns, port))) {
clone(tcp_splice_connect_ns,
ns_fn_stack + sizeof(ns_fn_stack) / 2,
CLONE_VM | CLONE_VFORK | CLONE_FILES | SIGCHLD,
(void *)&ns_arg);
return ns_arg.ret;
}
return tcp_splice_connect(c, conn, v6, port);
}
/**
* tcp_conn_from_sock() - Handle new connection request from listening socket
* @c: Execution context
* @ref: epoll reference of listening socket
* @now: Current timestamp
*/
static void tcp_conn_from_sock(struct ctx *c, union epoll_ref ref,
struct timespec *now)
{
union epoll_ref ref_conn = { .proto = IPPROTO_TCP,
.tcp.v6 = ref.tcp.v6 };
struct sockaddr_storage sa;
struct tcp_tap_conn *conn;
struct epoll_event ev;
socklen_t sa_len;
int s;
if (c->tcp.tap_conn_count >= MAX_TAP_CONNS)
return;
sa_len = sizeof(sa);
s = accept4(ref.s, (struct sockaddr *)&sa, &sa_len, SOCK_NONBLOCK);
if (s < 0)
return;
conn = &tt[c->tcp.tap_conn_count++];
ref_conn.tcp.index = conn - tt;
ref_conn.s = conn->sock = s;
if (ref.tcp.v6) {
struct sockaddr_in6 *sa6 = (struct sockaddr_in6 *)&sa;
if (IN6_IS_ADDR_LOOPBACK(&sa6->sin6_addr) ||
!memcmp(&sa6->sin6_addr, &c->addr6_seen, sizeof(c->addr6)))
memcpy(&sa6->sin6_addr, &c->gw6, sizeof(c->gw6));
memcpy(&conn->a.a6, &sa6->sin6_addr, sizeof(conn->a.a6));
conn->sock_port = ntohs(sa6->sin6_port);
conn->tap_port = ref.tcp.index;
conn->seq_to_tap = tcp_seq_init(c, AF_INET6, &sa6->sin6_addr,
conn->sock_port,
conn->tap_port,
now);
conn->seq_init_to_tap = conn->seq_to_tap;
tcp_hash_insert(c, conn, AF_INET6, &sa6->sin6_addr);
} else {
struct sockaddr_in *sa4 = (struct sockaddr_in *)&sa;
in_addr_t s_addr = ntohl(sa4->sin_addr.s_addr);
memset(&conn->a.a4.zero, 0, sizeof(conn->a.a4.zero));
memset(&conn->a.a4.one, 0xff, sizeof(conn->a.a4.one));
if (s_addr >> IN_CLASSA_NSHIFT == IN_LOOPBACKNET ||
s_addr == INADDR_ANY || s_addr == c->addr4_seen)
sa4->sin_addr.s_addr = c->gw4;
memcpy(&conn->a.a4.a, &sa4->sin_addr, sizeof(conn->a.a4.a));
conn->sock_port = ntohs(sa4->sin_port);
conn->tap_port = ref.tcp.index;
conn->seq_to_tap = tcp_seq_init(c, AF_INET, &sa4->sin_addr,
conn->sock_port,
conn->tap_port,
now);
conn->seq_init_to_tap = conn->seq_to_tap;
tcp_hash_insert(c, conn, AF_INET, &sa4->sin_addr);
}
conn->seq_ack_from_tap = conn->seq_to_tap + 1;
conn->tap_window = WINDOW_DEFAULT;
conn->ws_allowed = 1;
conn->ts_sock = conn->ts_tap = conn->ts_ack_tap = *now;
bitmap_set(tcp_act, conn - tt);
ev.events = EPOLLRDHUP;
ev.data.u64 = ref_conn.u64;
epoll_ctl(c->epollfd, EPOLL_CTL_ADD, conn->sock, &ev);
tcp_tap_state(conn, SOCK_SYN_SENT);
tcp_send_to_tap(c, conn, SYN, NULL, 0);
}
/**
* tcp_sock_handler_splice() - Handler for socket mapped to spliced connection
* @c: Execution context
* @ref: epoll reference
* @events: epoll events bitmap
*/
void tcp_sock_handler_splice(struct ctx *c, union epoll_ref ref,
uint32_t events)
{
int move_from, move_to, *pipes;
struct tcp_splice_conn *conn;
if (ref.tcp.listen) {
int s;
if (c->tcp.splice_conn_count >= MAX_SPLICE_CONNS)
return;
if ((s = accept4(ref.s, NULL, NULL, SOCK_NONBLOCK)) < 0)
return;
conn = &ts[c->tcp.splice_conn_count++];
conn->from = s;
tcp_splice_state(conn, SPLICE_ACCEPTED);
if (tcp_splice_new(c, conn, ref.tcp.v6, ref.tcp.index))
tcp_splice_destroy(c, conn);
return;
}
conn = &ts[ref.tcp.index];
if (events & EPOLLRDHUP || events & EPOLLHUP || events & EPOLLERR) {
tcp_splice_destroy(c, conn);
return;
}
if (events & EPOLLOUT) {
struct epoll_event ev = {
.events = EPOLLIN | EPOLLET | EPOLLRDHUP,
.data.u64 = ref.u64,
};
if (conn->state == SPLICE_CONNECT) {
tcp_splice_connect_finish(c, conn, ref.tcp.v6);
return;
}
epoll_ctl(c->epollfd, EPOLL_CTL_MOD, ref.s, &ev);
move_to = ref.s;
if (ref.s == conn->to) {
move_from = conn->from;
pipes = conn->pipe_from_to;
} else {
move_from = conn->to;
pipes = conn->pipe_to_from;
}
} else {
move_from = ref.s;
if (ref.s == conn->from) {
move_to = conn->to;
pipes = conn->pipe_from_to;
} else {
move_to = conn->from;
pipes = conn->pipe_to_from;
}
}
swap:
while (1) {
int retry_write = 1, no_read = 1;
ssize_t ret, nr = 0, nw;
retry:
ret = splice(move_from, NULL, pipes[1], NULL, PIPE_SIZE,
SPLICE_F_MOVE);
if (ret < 0) {
if (errno == EAGAIN) {
nr = PIPE_SIZE;
} else {
tcp_splice_destroy(c, conn);
return;
}
} else if (!ret && no_read) {
break;
} else if (ret) {
no_read = 0;
nr += ret;
}
nw = splice(pipes[0], NULL, move_to, NULL, nr, SPLICE_F_MOVE);
if (nw < 0) {
if (errno == EAGAIN) {
struct epoll_event ev = {
.events = EPOLLIN | EPOLLOUT | EPOLLET |
EPOLLRDHUP
};
if (no_read)
break;
if (retry_write--)
goto retry;
ref.s = move_to;
ev.data.u64 = ref.u64,
epoll_ctl(c->epollfd, EPOLL_CTL_MOD, move_to,
&ev);
break;
}
tcp_splice_destroy(c, conn);
return;
}
}
if ((events & (EPOLLIN | EPOLLOUT)) == (EPOLLIN | EPOLLOUT)) {
events = EPOLLIN;
SWAP(move_from, move_to);
if (pipes == conn->pipe_from_to)
pipes = conn->pipe_to_from;
else
pipes = conn->pipe_from_to;
goto swap;
}
}
/**
* tcp_sock_handler() - Handle new data from socket
* @c: Execution context
* @ref: epoll reference
* @events: epoll events bitmap
* @now: Current timestamp
*/
void tcp_sock_handler(struct ctx *c, union epoll_ref ref, uint32_t events,
struct timespec *now)
{
struct tcp_tap_conn *conn;
if (ref.tcp.splice) {
tcp_sock_handler_splice(c, ref, events);
return;
}
if (ref.tcp.listen) {
tcp_conn_from_sock(c, ref, now);
return;
}
conn = &tt[ref.tcp.index];
if (conn->state == LAST_ACK) {
tcp_send_to_tap(c, conn, ACK, NULL, 0);
tcp_tap_destroy(c, conn);
return;
}
if (conn->state == SOCK_SYN_SENT) {
/* This can only be a socket error or a shutdown from remote */
tcp_rst(c, conn);
return;
}
if (events & EPOLLERR) {
if (conn->state != CLOSED)
tcp_rst(c, conn);
return;
}
if (events & EPOLLOUT) { /* Implies TAP_SYN_SENT */
tcp_connect_finish(c, conn, ref);
return;
}
if (conn->state == ESTABLISHED)
tcp_data_from_sock(c, conn, now);
if (events & (EPOLLRDHUP | EPOLLHUP)) {
if (conn->state == ESTABLISHED) {
tcp_tap_state(conn, ESTABLISHED_SOCK_FIN);
shutdown(conn->sock, SHUT_RD);
tcp_data_from_sock(c, conn, now);
tcp_send_to_tap(c, conn, FIN | ACK, NULL, 0);
} else if (conn->state == FIN_WAIT_1) {
tcp_tap_state(conn, FIN_WAIT_1_SOCK_FIN);
shutdown(conn->sock, SHUT_RD);
tcp_data_from_sock(c, conn, now);
tcp_sock_consume(conn, conn->seq_ack_from_tap);
tcp_send_to_tap(c, conn, FIN | ACK, NULL, 0);
} else if (conn->state != ESTABLISHED_SOCK_FIN) {
tcp_tap_destroy(c, conn);
}
}
}
/**
* tcp_sock_init_ns() - Bind sockets in namespace for inbound connections
* @arg: Execution context
*
* Return: 0 on success, -1 on failure
*/
static int tcp_sock_init_ns(void *arg)
{
union tcp_epoll_ref tref = { .listen = 1, .splice = 1 };
struct ctx *c = (struct ctx *)arg;
in_port_t port;
ns_enter(c->pasta_pid);
if (c->v4) {
tref.v6 = 0;
for (port = 0; port < USHRT_MAX; port++) {
if (!bitmap_isset(c->tcp.port4_to_init, port))
continue;
tref.index = port;
sock_l4(c, AF_INET, IPPROTO_TCP, port, BIND_LOOPBACK,
tref.u32);
}
}
if (c->v6) {
tref.v6 = 1;
for (port = 0; port < USHRT_MAX; port++) {
if (!bitmap_isset(c->tcp.port6_to_init, port))
continue;
tref.index = port;
sock_l4(c, AF_INET6, IPPROTO_TCP, port, BIND_LOOPBACK,
tref.u32);
}
}
return 0;
}
/**
* tcp_sock_init() - Bind sockets for inbound connections, get key for sequence
* @c: Execution context
*
* Return: 0 on success, -1 on failure
*/
int tcp_sock_init(struct ctx *c)
{
union tcp_epoll_ref tref = { .listen = 1 };
char ns_fn_stack[NS_FN_STACK_SIZE];
enum bind_type tap_bind;
in_port_t port;
getrandom(&c->tcp.hash_secret, sizeof(c->tcp.hash_secret), GRND_RANDOM);
if (c->v4) {
tref.v6 = 0;
for (port = 0; port < USHRT_MAX; port++) {
tref.index = port;
if (bitmap_isset(c->tcp.port4_to_ns, port)) {
tref.splice = 1;
sock_l4(c, AF_INET, IPPROTO_TCP, port,
BIND_LOOPBACK, tref.u32);
tap_bind = BIND_EXT;
} else {
tap_bind = BIND_ANY;
}
if (bitmap_isset(c->tcp.port4_to_tap, port)) {
tref.splice = 0;
sock_l4(c, AF_INET, IPPROTO_TCP, port,
tap_bind, tref.u32);
}
}
tcp_sock4_iov_init();
}
if (c->v6) {
tref.v6 = 1;
for (port = 0; port < USHRT_MAX; port++) {
tref.index = port;
if (bitmap_isset(c->tcp.port6_to_ns, port)) {
tref.splice = 1;
sock_l4(c, AF_INET6, IPPROTO_TCP, port,
BIND_LOOPBACK, tref.u32);
tap_bind = BIND_EXT;
} else {
tap_bind = BIND_ANY;
}
if (bitmap_isset(c->tcp.port6_to_tap, port)) {
tref.splice = 0;
sock_l4(c, AF_INET6, IPPROTO_TCP, port,
tap_bind, tref.u32);
}
}
tcp_sock6_iov_init();
}
if (c->mode == MODE_PASTA) {
clone(tcp_sock_init_ns, ns_fn_stack + sizeof(ns_fn_stack) / 2,
CLONE_VM | CLONE_VFORK | CLONE_FILES | SIGCHLD,
(void *)c);
}
return 0;
}
/**
* tcp_timer_one() - Handler for timed events on one socket
* @c: Execution context
* @conn: Connection pointer
* @ts: Timestamp from caller
*/
static void tcp_timer_one(struct ctx *c, struct tcp_tap_conn *conn,
struct timespec *ts)
{
int ack_tap_ms = timespec_diff_ms(ts, &conn->ts_ack_tap);
int sock_ms = timespec_diff_ms(ts, &conn->ts_sock);
int tap_ms = timespec_diff_ms(ts, &conn->ts_tap);
switch (conn->state) {
case SOCK_SYN_SENT:
case TAP_SYN_RCVD:
if (ack_tap_ms > SYN_TIMEOUT)
tcp_rst(c, conn);
break;
case ESTABLISHED_SOCK_FIN:
if (ack_tap_ms > FIN_TIMEOUT) {
tcp_rst(c, conn);
break;
}
/* Falls through */
case ESTABLISHED:
if (tap_ms > ACT_TIMEOUT && sock_ms > ACT_TIMEOUT) {
tcp_rst(c, conn);
break;
}
if (conn->seq_to_tap == conn->seq_ack_from_tap &&
conn->seq_from_tap == conn->seq_ack_to_tap) {
conn->ts_sock = *ts;
break;
}
if (sock_ms > ACK_INTERVAL) {
if (conn->seq_from_tap > conn->seq_ack_to_tap)
tcp_send_to_tap(c, conn, 0, NULL, 0);
}
if (ack_tap_ms > ACK_TIMEOUT) {
if (conn->seq_ack_from_tap < conn->seq_to_tap) {
if (ack_tap_ms > 10 * ACK_TIMEOUT) {
tcp_rst(c, conn);
break;
}
conn->seq_to_tap = conn->seq_ack_from_tap;
if (sock_ms > ACK_TIMEOUT)
tcp_data_from_sock(c, conn, ts);
}
}
if (conn->seq_from_tap == conn->seq_ack_to_tap)
conn->ts_sock = *ts;
break;
case CLOSE_WAIT:
case FIN_WAIT_1:
if (sock_ms > FIN_TIMEOUT)
tcp_rst(c, conn);
break;
case FIN_WAIT_1_SOCK_FIN:
if (ack_tap_ms > FIN_TIMEOUT)
tcp_rst(c, conn);
break;
case LAST_ACK:
if (sock_ms > LAST_ACK_TIMEOUT)
tcp_rst(c, conn);
break;
case TAP_SYN_SENT:
case SPLICE_ACCEPTED:
case SPLICE_CONNECT:
case SPLICE_ESTABLISHED:
case CLOSED:
break;
}
}
/**
* tcp_timer() - Scan activity bitmap for sockets waiting for timed events
* @c: Execution context
* @ts: Timestamp from caller
*/
void tcp_timer(struct ctx *c, struct timespec *ts)
{
long *word = (long *)tcp_act, tmp;
unsigned int i;
int n;
for (i = 0; i < sizeof(tcp_act) / sizeof(long); i++, word++) {
tmp = *word;
while ((n = ffsl(tmp))) {
int index = i * sizeof(long) * 8 + n - 1;
tmp &= ~(1UL << (n - 1));
tcp_timer_one(c, &tt[index], ts);
}
}
}
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