# HG changeset patch # User Roman Arutyunyan <a...@nginx.com> # Date 1707472496 -14400 # Fri Feb 09 13:54:56 2024 +0400 # Node ID 9b89f44ddd3637afc939e31de348c7986ae9e76d # Parent 73eb75bee30f4aee66edfb500270dbb14710aafd 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. diff --git a/src/event/quic/ngx_event_quic_migration.c b/src/event/quic/ngx_event_quic_migration.c --- a/src/event/quic/ngx_event_quic_migration.c +++ b/src/event/quic/ngx_event_quic_migration.c @@ -925,12 +925,6 @@ 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; - - ngx_log_debug4(NGX_LOG_DEBUG_EVENT, c->log, 0, - "quic path seq:%uL send probe " - "mtu:%uz pnum:%uL tries:%ui", - path->seqnum, path->mtud, ctx->pnum, path->tries); log_error = c->log_error; c->log_error = NGX_ERROR_IGNORE_EMSGSIZE; @@ -943,14 +937,26 @@ 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] = ctx->pnum; + + ngx_log_debug4(NGX_LOG_DEBUG_EVENT, c->log, 0, + "quic path seq:%uL send probe " + "mtu:%uz pnum:%uL tries:%ui", + path->seqnum, path->mtud, ctx->pnum, path->tries); + + return NGX_OK; + } + + path->mtu_pnum[path->tries] = NGX_QUIC_UNSET_PN; + + 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; } _______________________________________________ nginx-devel mailing list nginx-devel@nginx.org https://mailman.nginx.org/mailman/listinfo/nginx-devel