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tcp: Don't set ACK flag while merely updating window value

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The receiver might take this as a duplicate ACK othewise.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
Stefano Brivio 2021-10-04 22:14:13 +02:00
parent 81128241d6
commit ffaf1d09f2
1 changed files with 19 additions and 15 deletions
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34
tcp.c
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@ -1273,6 +1273,7 @@ static int tcp_send_to_tap(struct ctx *c, struct tcp_tap_conn *conn, int flags,
{ {
char buf[sizeof(struct tcphdr) + OPT_MSS_LEN + OPT_WS_LEN + 1] = { 0 }; char buf[sizeof(struct tcphdr) + OPT_MSS_LEN + OPT_WS_LEN + 1] = { 0 };
uint32_t prev_ack_to_tap = conn->seq_ack_to_tap; uint32_t prev_ack_to_tap = conn->seq_ack_to_tap;
uint32_t prev_wnd_to_tap = conn->wnd_to_tap;
struct tcp_info info = { 0 }; struct tcp_info info = { 0 };
socklen_t sl = sizeof(info); socklen_t sl = sizeof(info);
int s = conn->sock; int s = conn->sock;
@ -1284,17 +1285,30 @@ static int tcp_send_to_tap(struct ctx *c, struct tcp_tap_conn *conn, int flags,
return 0; return 0;
if (conn->snd_buf < SNDBUF_SMALL) if (conn->snd_buf < SNDBUF_SMALL)
tcp_get_sndbuf(c, conn); tcp_get_sndbuf(conn);
if (getsockopt(s, SOL_TCP, TCP_INFO, &info, &sl)) { if (getsockopt(s, SOL_TCP, TCP_INFO, &info, &sl)) {
tcp_rst(c, conn); tcp_rst(c, conn);
return -ECONNRESET; return -ECONNRESET;
} }
if (!conn->local)
tcp_rtt_dst_check(conn, &info);
th = (struct tcphdr *)buf; th = (struct tcphdr *)buf;
data = (char *)(th + 1); data = (char *)(th + 1);
th->doff = sizeof(*th) / 4; th->doff = sizeof(*th) / 4;
if (conn->state > ESTABLISHED || (flags & (DUP_ACK | FORCE_ACK))) {
conn->seq_ack_to_tap = conn->seq_from_tap;
} else {
conn->seq_ack_to_tap = info.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;
}
if (flags & SYN) { if (flags & SYN) {
uint16_t mss; uint16_t mss;
@ -1338,23 +1352,13 @@ static int tcp_send_to_tap(struct ctx *c, struct tcp_tap_conn *conn, int flags,
th->ack = !!(flags & ACK); th->ack = !!(flags & ACK);
} else { } else {
th->ack = 1; th->ack = !!(flags & (ACK | FORCE_ACK | DUP_ACK)) ||
conn->seq_ack_to_tap != prev_ack_to_tap;
th->seq = htonl(conn->seq_to_tap); th->seq = htonl(conn->seq_to_tap);
} }
if (conn->state > ESTABLISHED || (flags & (DUP_ACK | FORCE_ACK))) { if (!flags && conn->seq_ack_to_tap == prev_ack_to_tap &&
conn->seq_ack_to_tap = conn->seq_from_tap; conn->wnd_to_tap == prev_wnd_to_tap)
} else {
conn->seq_ack_to_tap = info.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;
}
if (!flags &&
conn->seq_ack_to_tap == prev_ack_to_tap &&
c->tcp.kernel_snd_wnd && conn->wnd_to_tap == info.tcpi_snd_wnd)
return 0; return 0;
th->ack_seq = htonl(conn->seq_ack_to_tap); th->ack_seq = htonl(conn->seq_ack_to_tap);