From 22eac1ad6d22af0cba5aaae07dcaef59f049afae Mon Sep 17 00:00:00 2001
From: Thomas Eizinger <thomas@eizinger.io>
Date: Tue, 16 Sep 2025 20:27:47 +0000
Subject: [PATCH] ci: add latency to routers (#10352)

Now that we have a more realistic network setup in our compose file, we
can extend our router containers to apply the latency on the network
path. This means any use of the compose file has a latency by default,
simplifying our CI setup. It also allows us to restart containers
without having to re-apply the latency which is useful during
performance testing.
---
 .github/workflows/_integration_tests.yml | 10 ----------
 .github/workflows/ci.yml                 |  5 -----
 docker-compose.yml                       |  5 +++++
 scripts/router/router.sh                 |  8 ++++++++
 4 files changed, 13 insertions(+), 15 deletions(-)

diff --git a/.github/workflows/_integration_tests.yml b/.github/workflows/_integration_tests.yml
index 5b7a39d67..c48744cc1 100644
--- a/.github/workflows/_integration_tests.yml
+++ b/.github/workflows/_integration_tests.yml
@@ -170,16 +170,6 @@ jobs:
           sleep 3
 
           docker compose up veth-config
-      - name: Add 50ms simulated API latency
-        run: |
-          docker compose exec -T -u root api sh -c 'apk add --update --no-cache iproute2-tc'
-          docker compose exec -T -u root api sh -c 'tc qdisc add dev eth0 root netem delay 50ms'
-
-      - name: Add 10ms simulated gateway latency
-        run: |
-          # compatibility test images won't have the `tc` command
-          docker compose exec -T gateway sh -c 'apk add --update --no-cache iproute2-tc'
-          docker compose exec -T gateway sh -c 'tc qdisc add dev eth0 root netem delay 10ms'
 
       - run: ./scripts/tests/${{ matrix.test.script }}.sh
 
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 71b630aca..481ab49a2 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -336,11 +336,6 @@ jobs:
           docker compose up -d gateway --no-build
           docker compose up -d client --no-build
           docker compose up veth-config
-      - name: Add 10ms simulated latency
-        run: |
-          docker compose exec -T client tc qdisc add dev eth0 root netem delay 10ms
-          docker compose exec -T gateway tc qdisc add dev eth0 root netem delay 10ms
-          docker compose exec -T relay-1 tc qdisc add dev eth0 root netem delay 10ms
       - name: "Performance test: ${{ matrix.flavour }}-${{ matrix.test }}"
         timeout-minutes: 5
         env:
diff --git a/docker-compose.yml b/docker-compose.yml
index 8c2bd9f05..56a1bf88d 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -104,6 +104,7 @@ services:
         8081 172.28.0.100 tcp
         8081 172:28:0::100 tcp
       MASQUERADE_TYPE: ""
+      NETWORK_LATENCY_MS: 50
     networks:
       app-internal:
         ipv4_address: 172.28.0.254
@@ -225,6 +226,7 @@ services:
       service: router
     environment:
       MASQUERADE_TYPE: ${CLIENT_MASQUERADE:-}
+      NETWORK_LATENCY_MS: 10
     networks:
       client-internal:
         ipv4_address: 172.30.0.254
@@ -298,6 +300,7 @@ services:
       service: router
     environment:
       MASQUERADE_TYPE: ${GATEWAY_MASQUERADE:-}
+      NETWORK_LATENCY_MS: 10
     networks:
       gateway-internal:
         ipv4_address: 172.31.0.254
@@ -342,6 +345,7 @@ services:
         49152-65535 172.29.1.100 udp
         3478 172:29:1::100 udp
         49152-65535 172:29:1::100 udp
+      NETWORK_LATENCY_MS: 30
     networks:
       relay-1-internal:
         ipv4_address: 172.29.1.254
@@ -388,6 +392,7 @@ services:
         49152-65535 172.29.2.100 udp
         3478 172:29:2::100 udp
         49152-65535 172:29:2::100 udp
+      NETWORK_LATENCY_MS: 30
     networks:
       relay-2-internal:
         ipv4_address: 172.29.2.254
diff --git a/scripts/router/router.sh b/scripts/router/router.sh
index bf1397525..8731e85bb 100644
--- a/scripts/router/router.sh
+++ b/scripts/router/router.sh
@@ -64,6 +64,14 @@ if [ -n "${PORT_FORWARDS:-}" ]; then
     done
 fi
 
+# Add configurable latency if specified
+if [ -n "${NETWORK_LATENCY_MS:-}" ]; then
+    LATENCY=$((NETWORK_LATENCY_MS / 2)) # Latency is only applied to outbound packets. To achieve the actual configured latency, we apply half of it to each interface.
+
+    tc qdisc add dev internet root netem delay "${LATENCY}ms"
+    tc qdisc add dev internal root netem delay "${LATENCY}ms"
+fi
+
 echo "-----------------------------------------------------------------------------------------------"
 cat "$CONFIG_FILE"
 echo "-----------------------------------------------------------------------------------------------"