socket-util: make recvmsg_safe() handle MSG_TRUNC too

Also, unify MSG_TRUNC handling all across the codebase.

src/basic/socket-util.c

@@ -1447,18 +1447,22 @@ int socket_bind_to_ifindex(int fd, int ifindex) {
 ssize_t recvmsg_safe(int sockfd, struct msghdr *msg, int flags) {
         ssize_t n;
 
-        /* A wrapper around recvmsg() that checks for MSG_CTRUNC, and turns it into an error, in a reasonably
-         * safe way, closing any SCM_RIGHTS fds in the error path.
+        /* A wrapper around recvmsg() that checks for MSG_CTRUNC and MSG_TRUNC, and turns them into an error,
+         * in a reasonably safe way, closing any received fds in the error path.
          *
          * Note that unlike our usual coding style this might modify *msg on failure. */
 
+        assert(sockfd >= 0);
+        assert(msg);
+
         n = recvmsg(sockfd, msg, flags);
         if (n < 0)
                 return -errno;
 
-        if (FLAGS_SET(msg->msg_flags, MSG_CTRUNC)) {
+        if (FLAGS_SET(msg->msg_flags, MSG_CTRUNC) ||
+            (!FLAGS_SET(flags, MSG_PEEK) && FLAGS_SET(msg->msg_flags, MSG_TRUNC))) {
                 cmsg_close_all(msg);
-                return -EXFULL; /* a recognizable error code */
+                return FLAGS_SET(msg->msg_flags, MSG_CTRUNC) ? -ECHRNG : -EXFULL;
         }
 
         return n;

src/basic/socket-util.h

@@ -329,7 +329,7 @@ struct timespec_large {
 
 /* glibc duplicates timespec/timeval on certain 32-bit arches, once in 32-bit and once in 64-bit.
  * See __convert_scm_timestamps() in glibc source code. Hence, we need additional buffer space for them
- * to prevent from recvmsg_safe() returning -EXFULL. */
+ * to prevent truncating control msg (recvmsg() MSG_CTRUNC). */
 #define CMSG_SPACE_TIMEVAL                                              \
         ((sizeof(struct timeval) == sizeof(struct timeval_large)) ?     \
          CMSG_SPACE(sizeof(struct timeval)) :                           \