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When available, we want to retrieve our socket peer's advertised window and forward that to the guest. That information has been available from the kernel via the TCP_INFO getsockopt() since kernel commit 8f7baad7f035. Currently our probing for this is a bit odd. The HAS_SND_WND define determines if our headers include the tcp_snd_wnd field, but that doesn't necessarily mean the running kernel supports it. Currently we start by assuming it's _not_ available, but mark it as available if we ever see a non-zero value in the field. This is a bit hit and miss in two ways: * Zero is perfectly possible window the peer could report, so we can get false negatives * We're reading TCP_INFO into a local variable, which might not be zero initialised, so if the kernel _doesn't_ write it it could have non-zero garbage, giving us false positives. We can use a more direct way of probing for this: getsockopt() reports the length of the information retreived. So, check whether that's long enough to include the field. This lets us probe the availability of the field once and for all during initialisation. That in turn allows ctx to become a const pointer to tcp_prepare_flags() which cascades through many other functions. We also move the flag for the probe result from the ctx structure to a global, to match peek_offset_cap. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
101 lines
2.9 KiB
C
101 lines
2.9 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later
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* Copyright (c) 2021 Red Hat GmbH
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* Author: Stefano Brivio <sbrivio@redhat.com>
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*/
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#ifndef TCP_INTERNAL_H
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#define TCP_INTERNAL_H
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#define MAX_WS 8
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#define MAX_WINDOW (1 << (16 + (MAX_WS)))
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#define MSS4 ROUND_DOWN(IP_MAX_MTU - \
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sizeof(struct tcphdr) - \
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sizeof(struct iphdr), \
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sizeof(uint32_t))
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#define MSS6 ROUND_DOWN(IP_MAX_MTU - \
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sizeof(struct tcphdr) - \
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sizeof(struct ipv6hdr), \
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sizeof(uint32_t))
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#define SEQ_LE(a, b) ((b) - (a) < MAX_WINDOW)
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#define SEQ_LT(a, b) ((b) - (a) - 1 < MAX_WINDOW)
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#define SEQ_GE(a, b) ((a) - (b) < MAX_WINDOW)
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#define SEQ_GT(a, b) ((a) - (b) - 1 < MAX_WINDOW)
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#define FIN (1 << 0)
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#define SYN (1 << 1)
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#define RST (1 << 2)
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#define ACK (1 << 4)
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/* Flags for internal usage */
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#define DUP_ACK (1 << 5)
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#define OPT_EOL 0
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#define OPT_NOP 1
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#define OPT_MSS 2
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#define OPT_MSS_LEN 4
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#define OPT_WS 3
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#define OPT_WS_LEN 3
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#define OPT_SACKP 4
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#define OPT_SACK 5
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#define OPT_TS 8
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#define TAPSIDE(conn_) ((conn_)->f.pif[1] == PIF_TAP)
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#define TAPFLOW(conn_) (&((conn_)->f.side[TAPSIDE(conn_)]))
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#define TAP_SIDX(conn_) (FLOW_SIDX((conn_), TAPSIDE(conn_)))
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#define CONN_V4(conn) (!!inany_v4(&TAPFLOW(conn)->oaddr))
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#define CONN_V6(conn) (!CONN_V4(conn))
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/*
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* enum tcp_iov_parts - I/O vector parts for one TCP frame
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* @TCP_IOV_TAP tap backend specific header
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* @TCP_IOV_ETH Ethernet header
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* @TCP_IOV_IP IP (v4/v6) header
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* @TCP_IOV_PAYLOAD IP payload (TCP header + data)
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* @TCP_NUM_IOVS the number of entries in the iovec array
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*/
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enum tcp_iov_parts {
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TCP_IOV_TAP = 0,
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TCP_IOV_ETH = 1,
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TCP_IOV_IP = 2,
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TCP_IOV_PAYLOAD = 3,
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TCP_NUM_IOVS
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};
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extern char tcp_buf_discard [MAX_WINDOW];
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void conn_flag_do(const struct ctx *c, struct tcp_tap_conn *conn,
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unsigned long flag);
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#define conn_flag(c, conn, flag) \
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do { \
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flow_trace(conn, "flag at %s:%i", __func__, __LINE__); \
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conn_flag_do(c, conn, flag); \
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} while (0)
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void conn_event_do(const struct ctx *c, struct tcp_tap_conn *conn,
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unsigned long event);
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#define conn_event(c, conn, event) \
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do { \
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flow_trace(conn, "event at %s:%i", __func__, __LINE__); \
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conn_event_do(c, conn, event); \
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} while (0)
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void tcp_rst_do(const struct ctx *c, struct tcp_tap_conn *conn);
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#define tcp_rst(c, conn) \
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do { \
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flow_dbg((conn), "TCP reset at %s:%i", __func__, __LINE__); \
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tcp_rst_do(c, conn); \
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} while (0)
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size_t tcp_l2_buf_fill_headers(const struct tcp_tap_conn *conn,
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struct iovec *iov, size_t dlen,
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const uint16_t *check, uint32_t seq);
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int tcp_update_seqack_wnd(const struct ctx *c, struct tcp_tap_conn *conn,
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int force_seq, struct tcp_info *tinfo);
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int tcp_prepare_flags(const struct ctx *c, struct tcp_tap_conn *conn, int flags,
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struct tcphdr *th, char *data, size_t *optlen);
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#endif /* TCP_INTERNAL_H */
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