45 lines
1.6 KiB
Diff
45 lines
1.6 KiB
Diff
From 2d5181f7363a09b24b225b9d7c07f999a1f89e63 Mon Sep 17 00:00:00 2001
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From: Stefano Brivio <sbrivio@redhat.com>
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Date: Mon, 3 Feb 2025 08:19:16 +0100
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Subject: [PATCH] tcp: Don't reset outbound connection on SYN retries
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Reported by somebody on IRC: if the server has considerable latency,
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it might happen that the client retries sending SYN segments for the
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same flow while we're still in a TAP_SYN_RCVD, non-ESTABLISHED state.
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In that case, we should go with the blanket assumption that we need
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to reset the connection on any unexpected segment: RFC 9293 explicitly
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mentions this case in Figure 8: Recovery from Old Duplicate SYN,
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section 3.5. It doesn't make sense for us to set a specific sequence
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number, socket-side, but we should definitely wait and see.
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Ignoring the duplicate SYN segment should also be compatible with
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section 3.10.7.3. SYN-SENT STATE, which mentions updating sequences
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socket-side (which we can't do anyway), but certainly not reset the
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connection.
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Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
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Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
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(cherry picked from commit 722d347c1932f630a53ba05ea0270a651ed601b2)
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---
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tcp.c | 3 +++
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1 file changed, 3 insertions(+)
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diff --git a/tcp.c b/tcp.c
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index bbc5687..babd02a 100644
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--- a/tcp.c
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+++ b/tcp.c
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@@ -1962,6 +1962,9 @@ int tcp_tap_handler(struct ctx *c, uint8_t pif, sa_family_t af,
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/* Establishing connection from tap */
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if (conn->events & TAP_SYN_RCVD) {
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+ if (th->syn && !th->ack && !th->fin)
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+ return 1; /* SYN retry: ignore and keep waiting */
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+
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if (!(conn->events & TAP_SYN_ACK_SENT))
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goto reset;
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--
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2.47.1
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