test: skip the symlink part of test_touch_file() in containers

Our (RHEL 8) touch_file() is not clever enough and does chmod() on a
symlink, which fails with EOPNOTSUPP on newer kernels. This is not an
issue on the RHEL 8 kernel, where doing chmod() on a symlink works
(albeit only on tmpfs) but in GH Actions we run in a container, and with
the underlying kernel doing chmod() on a symlink fails even on tmpfs:

RHEL 8:
~# mount -t tmpfs tmpfs /tmp
~# (cd /tmp; ln -s symlink dangling; ln -s /etc/os-release symlink)
~# (cd /var/tmp; ln -s symlink dangling; ln -s /etc/os-release symlink)
~# gcc -o main main.c -D_GNU_SOURCE
~# ./main /tmp/dangling
chmod(/proc/self/fd/3)=0 (0)
~# ./main /tmp/symlink
chmod(/proc/self/fd/3)=0 (0)
~# ./main /var/tmp/dangling
chmod(/proc/self/fd/3)=-1 (95)
~# ./main /var/tmp/symlink
chmod(/proc/self/fd/3)=-1 (95)

Newer kernel:
~# uname -r
6.7.4-200.fc39.x86_64
~# ./main /tmp/dangling
chmod(/proc/self/fd/3)=-1 (95)
~# ./main /tmp/symlink
chmod(/proc/self/fd/3)=-1 (95)
~# ./main /var/tmp/dangling
chmod(/proc/self/fd/3)=-1 (95)
~# ./main /var/tmp/symlink
chmod(/proc/self/fd/3)=-1 (95)

Backporting the necessary patches would be way too risky so late in the
RHEL 8 cycle, so let's just skip the offending test when running in a
container. This should work around this issue in GH Actions, but still
run the test on C8S/RHEL8 machines.

See: redhat-plumbers#434

RHEL-only

.github/workflows/unit_tests.sh

@@ -159,7 +159,7 @@ for phase in "${PHASES[@]}"; do
             # unexpected fails due to incompatibilities with older systemd
             $DOCKER_EXEC ninja -C build install
             docker restart $CONT_NAME
-            $DOCKER_EXEC ninja -C build test
+            docker exec --interactive=false -e GITHUB_ACTIONS=1 -t $CONT_NAME ninja -C build test
             ;;
         RUN_ASAN|RUN_GCC_ASAN|RUN_CLANG_ASAN)
             if [[ "$phase" = "RUN_CLANG_ASAN" ]]; then
@@ -173,6 +173,7 @@ for phase in "${PHASES[@]}"; do
             docker exec --interactive=false \
                 -e UBSAN_OPTIONS=print_stacktrace=1:print_summary=1:halt_on_error=1 \
                 -e ASAN_OPTIONS=strict_string_checks=1:detect_stack_use_after_return=1:check_initialization_order=1:strict_init_order=1 \
+                -e GITHUB_ACTIONS=1
                 -t $CONT_NAME \
                 meson test --timeout-multiplier=3 -C ./build/ --print-errorlogs
             ;;

src/test/test-fs-util.c

@@ -15,6 +15,7 @@
 #include "stdio-util.h"
 #include "string-util.h"
 #include "strv.h"
+#include "tests.h"
 #include "user-util.h"
 #include "util.h"
 #include "virt.h"
@@ -544,15 +545,17 @@ static void test_touch_file(void) {
                 assert_se(timespec_load(&st.st_mtim) == test_mtime);
         }
 
-        a = strjoina(p, "/lnk");
-        assert_se(symlink("target", a) >= 0);
-        assert_se(touch_file(a, false, test_mtime, test_uid, test_gid, 0640) >= 0);
-        assert_se(lstat(a, &st) >= 0);
-        assert_se(st.st_uid == test_uid);
-        assert_se(st.st_gid == test_gid);
-        assert_se(S_ISLNK(st.st_mode));
-        assert_se((st.st_mode & 0777) == 0640);
-        assert_se(timespec_load(&st.st_mtim) == test_mtime);
+        if (streq_ptr(ci_environment(), "github_actions")) {
+                a = strjoina(p, "/lnk");
+                assert_se(symlink("target", a) >= 0);
+                assert_se(touch_file(a, false, test_mtime, test_uid, test_gid, 0640) >= 0);
+                assert_se(lstat(a, &st) >= 0);
+                assert_se(st.st_uid == test_uid);
+                assert_se(st.st_gid == test_gid);
+                assert_se(S_ISLNK(st.st_mode));
+                assert_se((st.st_mode & 0777) == 0640);
+                assert_se(timespec_load(&st.st_mtim) == test_mtime);
+        }
 }
 
 static void test_unlinkat_deallocate(void) {