Resolve symlinks in log_tail_init so inotify watches real file

inotify watches the symlink inode itself, not the target, so IN_MODIFY
never fires when the target file is written. Use realpath() to resolve
the configured path before open() and inotify_add_watch(), allowing
a stable symlink (e.g. current.log) in the unit YAML that gets
re-resolved to the actual log file on each init/SIGHUP.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 12 insertions, 7 deletions

diff --git a/src/log_tail.c b/src/log_tail.c
index 973cc0b..c238911 100644
--- a/src/log_tail.c
+++ b/src/log_tail.c
@@ -35,9 +35,14 @@ void log_tail_init(void) {
         for (int j = 0; j < u->log_count; j++) {
             const char *path = u->log_paths[j];
             if (!path[0]) continue;
-            int log_fd = open(path, O_RDONLY | O_NONBLOCK | O_CLOEXEC);
+            /* Resolve symlinks so inotify watches the real file, not the link */
+            char resolved[MAX_PATH];
+            const char *open_path = path;
+            if (realpath(path, resolved) != NULL)
+                open_path = resolved;
+            int log_fd = open(open_path, O_RDONLY | O_NONBLOCK | O_CLOEXEC);
             if (log_fd < 0) {
-                log_warn("log_tail: cannot open %s: %s", path, strerror(errno));
+                log_warn("log_tail: cannot open %s: %s", open_path, strerror(errno));
                 continue;
             }
             lseek(log_fd, 0, SEEK_END);
@@ -47,17 +52,17 @@ void log_tail_init(void) {
                 close(log_fd);
                 continue;
             }
-            int wd = inotify_add_watch(ifd, path,
+            int wd = inotify_add_watch(ifd, open_path,
                                        IN_MODIFY | IN_MOVE_SELF | IN_DELETE_SELF);
             if (wd < 0) {
                 log_warn("log_tail: inotify_add_watch %s: %s",
-                         path, strerror(errno));
+                         open_path, strerror(errno));
                 close(ifd);
                 close(log_fd);
                 continue;
             }
             if (watch_count >= MAX_LOG_WATCHES) {
-                log_warn("log_tail: max watches reached, skipping %s", path);
+                log_warn("log_tail: max watches reached, skipping %s", open_path);
                 close(ifd);
                 close(log_fd);
                 continue;
@@ -66,13 +71,13 @@ void log_tail_init(void) {
             watches[watch_count].watch_wd   = wd;
             watches[watch_count].log_fd     = log_fd;
             watches[watch_count].unit       = u;
-            strncpy(watches[watch_count].path, path, MAX_PATH - 1);
+            strncpy(watches[watch_count].path, open_path, MAX_PATH - 1);
             watch_count++;
             struct epoll_event ev;
             ev.events  = EPOLLIN;
             ev.data.fd = ifd;
             epoll_ctl(g.epoll_fd, EPOLL_CTL_ADD, ifd, &ev);
-            log_info("log_tail: watching %s for unit %s", path, u->name);
+            log_info("log_tail: watching %s for unit %s", open_path, u->name);
         }
     }
 }