Welcome! Log In Create A New Profile

Advanced

[nginx] QUIC: fixed unsent MTU probe acknowledgement.

Roman Arutyunyan
February 14, 2024 09:12AM
details: https://hg.nginx.org/nginx/rev/2ed3f57dca0a
branches:
changeset: 9208:2ed3f57dca0a
user: Roman Arutyunyan <arut@nginx.com>
date: Wed Feb 14 16:56:28 2024 +0400
description:
QUIC: fixed unsent MTU probe acknowledgement.

Previously if an MTU probe send failed early in ngx_quic_frame_sendto()
due to allocation error or congestion control, the application level packet
number was not increased, but was still saved as MTU probe packet number.
Later when a packet with this number was acknowledged, the unsent MTU probe
was acknowledged as well. This could result in discovering a bigger MTU than
supported by the path, which could lead to EMSGSIZE (Message too long) errors
while sending further packets.

The problem existed since PMTUD was introduced in 58afcd72446f (1.25.2).
Back then only the unlikely memory allocation error could trigger it. However
in efcdaa66df2e congestion control was added to ngx_quic_frame_sendto() which
can now trigger the issue with a higher probability.

diffstat:

src/event/quic/ngx_event_quic_migration.c | 19 ++++++++++++-------
1 files changed, 12 insertions(+), 7 deletions(-)

diffs (53 lines):

diff -r 73eb75bee30f -r 2ed3f57dca0a src/event/quic/ngx_event_quic_migration.c
--- a/src/event/quic/ngx_event_quic_migration.c Tue Jan 30 19:19:26 2024 +0400
+++ b/src/event/quic/ngx_event_quic_migration.c Wed Feb 14 16:56:28 2024 +0400
@@ -909,6 +909,7 @@ static ngx_int_t
ngx_quic_send_path_mtu_probe(ngx_connection_t *c, ngx_quic_path_t *path)
{
size_t mtu;
+ uint64_t pnum;
ngx_int_t rc;
ngx_uint_t log_error;
ngx_quic_frame_t *frame;
@@ -925,7 +926,7 @@ ngx_quic_send_path_mtu_probe(ngx_connect

qc = ngx_quic_get_connection(c);
ctx = ngx_quic_get_send_ctx(qc, ssl_encryption_application);
- path->mtu_pnum[path->tries] = ctx->pnum;
+ pnum = ctx->pnum;

ngx_log_debug4(NGX_LOG_DEBUG_EVENT, c->log, 0,
"quic path seq:%uL send probe "
@@ -943,14 +944,18 @@ ngx_quic_send_path_mtu_probe(ngx_connect
path->mtu = mtu;
c->log_error = log_error;

+ if (rc == NGX_OK) {
+ path->mtu_pnum[path->tries] = pnum;
+ return NGX_OK;
+ }
+
+ ngx_log_debug2(NGX_LOG_DEBUG_EVENT, c->log, 0,
+ "quic path seq:%uL rejected mtu:%uz",
+ path->seqnum, path->mtud);
+
if (rc == NGX_ERROR) {
if (c->write->error) {
c->write->error = 0;
-
- ngx_log_debug2(NGX_LOG_DEBUG_EVENT, c->log, 0,
- "quic path seq:%uL rejected mtu:%uz",
- path->seqnum, path->mtud);
-
return NGX_DECLINED;
}

@@ -976,7 +981,7 @@ ngx_quic_handle_path_mtu(ngx_connection_
pnum = path->mtu_pnum[i];

if (pnum == NGX_QUIC_UNSET_PN) {
- break;
+ continue;
}

if (pnum < min || pnum > max) {
_______________________________________________
nginx-devel mailing list
nginx-devel@nginx.org
https://mailman.nginx.org/mailman/listinfo/nginx-devel
Subject Author Views Posted

[nginx] QUIC: fixed unsent MTU probe acknowledgement.

Roman Arutyunyan 239 February 14, 2024 09:12AM



Sorry, you do not have permission to post/reply in this forum.

Online Users

Guests: 340
Record Number of Users: 8 on April 13, 2023
Record Number of Guests: 500 on July 15, 2024
Powered by nginx      Powered by FreeBSD      PHP Powered      Powered by MariaDB      ipv6 ready