From f3b6ae0b36fdee26a6a7be00315e2183bc70f1ef Mon Sep 17 00:00:00 2001 From: Misha Kav Date: Thu, 30 Jul 2026 13:22:07 +0300 Subject: [PATCH] fix: set dind MTU in the GitLab-hosted CI template [LINBEE-27634] GitLab-hosted runners attach the dind container's network at MTU 1360, but the Docker daemon inside dind defaults its bridge to 1500. Oversized packets are then dropped silently, so requests from the rules engine connect at TCP and hang in the TLS handshake until the client times out - jobs sat for 15-30 minutes and produced no review. Measured on a GitLab-hosted runner, identical containers and endpoint: MTU 1500 -> 4/4 requests stalled 40s MTU 1360 -> 0/4 stalled, 261ms each End to end, one job went from 17.5 minutes to 83 seconds. The Kubernetes template already sets --mtu (1450, correct for a VXLAN overlay) and is left alone; the shell template is untouched since self-managed hosts are usually 1500 and lowering it there would only cost throughput. Ref: https://support.gitlab.com/hc/en-us/articles/27528955698972 Co-Authored-By: Claude Opus 5 (1M context) --- docs/downloads/gitlab-ci.yml | 1 + 1 file changed, 1 insertion(+) diff --git a/docs/downloads/gitlab-ci.yml b/docs/downloads/gitlab-ci.yml index 3b395381d..f4a952d0b 100644 --- a/docs/downloads/gitlab-ci.yml +++ b/docs/downloads/gitlab-ci.yml @@ -11,6 +11,7 @@ image: docker:latest services: - name: docker:dind + command: ["--mtu=1360"] before_script: - docker login -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD" $CI_REGISTRY