socat CI: run the test suite as parallel netns shards

The socat suite is sleep-bound and slow run serially. Drive it through
parallel-make-check.py as ~6 shards per CPU, 2 running per CPU at once: each
shard runs a round-robin slice of the tests in its own bwrap network
namespace (so parallel shards don't collide on ports) and its own build-dir
copy. The work is almost all waiting, so the oversubscription just overlaps
the waits.

Install bubblewrap so the netns isolation actually happens (without it the
runner silently shares one namespace and the shards collide). Each fresh
netns is IPv4-loopback only, so re-create IPv6 loopback (CAP_NET_ADMIN) for
the ::1 / dual-stack tests, and add non-loopback placeholders (fc00::1,
192.0.2.1) so glibc's AI_ADDRCONFIG still returns both families - without
them socat's getaddrinfo fails on numeric non-loopback addresses, e.g. the
multicast tests. Relax the AppArmor unprivileged-userns restriction so the
bwrap netns + CAP_NET_ADMIN work on ubuntu-24.04.

.github/workflows/socat.yml

@@ -39,10 +39,11 @@ jobs:
 
 
   socat_check:
+    name: socat ${{ matrix.socat_version }}
     if: ${{ (github.repository_owner == 'wolfssl') && (github.event_name != 'pull_request' || github.event.pull_request.draft == false) }}
     runs-on: ubuntu-24.04
-    # This should be a safe limit for the tests to run.
-    timeout-minutes: 30
+    # This should be a safe limit for the parallel tests to run.
+    timeout-minutes: 15
     needs: build_wolfssl
     strategy:
       fail-fast: false
@@ -56,13 +57,15 @@ jobs:
       - name: Checkout wolfSSL CI actions
         uses: actions/checkout@v5
         with:
-          sparse-checkout: .github/actions
+          sparse-checkout: |
+            .github/actions
+            .github/scripts
           fetch-depth: 1
 
       - name: Install prereqs
         uses: ./.github/actions/install-apt-deps
         with:
-          packages: build-essential autoconf libtool pkg-config clang libc++-dev
+          packages: build-essential autoconf libtool pkg-config clang libc++-dev bubblewrap
           ghcr-debs-tag: ubuntu-24.04-full
 
       - name: Download lib
@@ -91,9 +94,48 @@ jobs:
           ./configure --with-wolfssl=$GITHUB_WORKSPACE/build-dir --enable-default-ipv=4
           make -j
 
+      # Ubuntu 24.04 can restrict unprivileged user namespaces via AppArmor,
+      # which leaves CAP_NET_ADMIN ineffective inside bwrap's netns; the shards
+      # need it to re-create IPv6 loopback there. Relax the restriction.
+      - name: Allow unprivileged user namespaces (for bwrap)
+        run: sudo sysctl -w kernel.apparmor_restrict_unprivileged_userns=0 || true
+
       - name: Run socat tests
-        working-directory: ./socat-${{ matrix.socat_version }}
+        env:
+          SOCAT_SRC: ${{ github.workspace }}/socat-${{ matrix.socat_version }}
+          EXPECT_FAIL: ${{ matrix.expect_fail }}
         run: |
           export LD_LIBRARY_PATH=$GITHUB_WORKSPACE/build-dir/lib:$LD_LIBRARY_PATH
-          export SHELL=/bin/bash
-          SOCAT=$GITHUB_WORKSPACE/socat-${{ matrix.socat_version }}/socat ./test.sh -t 1.0 --expect-fail ${{ matrix.expect_fail }}
+          # The socat suite is sleep-bound, so run it as parallel shards via the
+          # shared parallel runner. The work is almost all waiting (timeouts and
+          # sleeps; only ~16% CPU even when packed), so oversubscribe: ~6 shards
+          # per CPU below, run 2 per CPU at once (--threads), so several overlap
+          # their waits (bigger runners get proportionally more). Each shard runs
+          # a round-robin slice of the tests ($SHARD/$SHARDS) in its own bwrap
+          # network namespace (no port collisions) and its own build-dir copy.
+          # ${tests:-0} keeps a shard that drew no test numbers a no-op (test 0
+          # matches nothing) instead of letting test.sh fall back to running the
+          # whole suite.
+          #
+          # bwrap --unshare-net gives each shard a fresh netns with loopback up
+          # but IPv4-only; re-create IPv6 loopback (CAP_NET_ADMIN is granted by
+          # the runner) so the suite's ::1 / dual-stack tests work as in the host
+          # namespace. fc00::1 and 192.0.2.1 are non-loopback placeholders so
+          # glibc's AI_ADDRCONFIG still returns IPv6/IPv4: with only loopback
+          # configured it drops the family, and socat's getaddrinfo then fails on
+          # numeric non-loopback addresses (e.g. the multicast tests). Best-effort
+          # (|| true), errors left visible so a runner without IPv6 still runs the
+          # IPv4 tests and any failure stays diagnosable in the log.
+          cat > socat-configs.json <<'EOF'
+          [{
+            "name": "socat", "build": false, "netns": true, "shards": __SHARDS__,
+            "run": [["bash", "-c", "set -e; ip link set lo up || true; sysctl -wq net.ipv6.conf.lo.disable_ipv6=0 || true; ip addr add ::1/128 dev lo || true; ip addr add fc00::1/128 dev lo || true; ip addr add 192.0.2.1/32 dev lo || true; sysctl -wq net.ipv6.bindv6only=0 || true; cp -a \"$SOCAT_SRC/.\" .; tests=$(seq \"$SHARD\" \"$SHARDS\" 999); SOCAT=\"$PWD/socat\" SHELL=/bin/bash ./test.sh -t 1.0 --expect-fail \"$EXPECT_FAIL\" ${tests:-0}"]]
+          }]
+          EOF
+          sed -i "s/__SHARDS__/$(( 6 * $(nproc) ))/" socat-configs.json
+          # Run 2 shards per CPU at once: the per-shard netns isolates ports, so
+          # the only real cost of overlap is CPU, and the suite barely uses any
+          # (mostly waiting), so this just overlaps the waits. fail-fast (the
+          # default) aborts the rest on the first failure.
+          .github/scripts/parallel-make-check.py \
+            --threads "$(( 2 * $(nproc) ))" socat-configs.json