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QUIC: fixed unsent MTU probe acknowledgement.

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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.
This commit is contained in:
Roman Arutyunyan 2024-02-14 16:56:28 +04:00
parent 71a0a4acdb
commit ed47f72a85
1 changed files with 12 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
src/event/quic/ngx_event_quic_migration.c
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@ -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_connection_t *c, ngx_quic_path_t *path)
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_connection_t *c, ngx_quic_path_t *path)
path->mtu = mtu;
c->log_error = log_error;
if (rc == NGX_ERROR) {
if (c->write->error) {
c->write->error = 0;
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;
return NGX_DECLINED;
}
@ -976,7 +981,7 @@ ngx_quic_handle_path_mtu(ngx_connection_t *c, ngx_quic_path_t *path,
pnum = path->mtu_pnum[i];
if (pnum == NGX_QUIC_UNSET_PN) {
break;
continue;
}
if (pnum < min || pnum > max) {