Merge pull request #15570 from poettering/cmsg-find

CMSG_FIND_DATA() and cmsg_find() work

src/basic/socket-util.c

@@ -887,7 +887,7 @@ ssize_t receive_one_fd_iov(
                 .msg_iov = iov,
                 .msg_iovlen = iovlen,
         };
-        struct cmsghdr *cmsg, *found = NULL;
+        struct cmsghdr *found;
         ssize_t k;
 
         assert(transport_fd >= 0);
@@ -905,16 +905,7 @@ ssize_t receive_one_fd_iov(
         if (k < 0)
                 return k;
 
-        CMSG_FOREACH(cmsg, &mh) {
-                if (cmsg->cmsg_level == SOL_SOCKET &&
-                    cmsg->cmsg_type == SCM_RIGHTS &&
-                    cmsg->cmsg_len == CMSG_LEN(sizeof(int))) {
-                        assert(!found);
-                        found = cmsg;
-                        break;
-                }
-        }
-
+        found = cmsg_find(&mh, SOL_SOCKET, SCM_RIGHTS, CMSG_LEN(sizeof(int)));
         if (!found) {
                 cmsg_close_all(&mh);
 

src/basic/socket-util.h

@@ -158,6 +158,14 @@ int flush_accept(int fd);
 
 struct cmsghdr* cmsg_find(struct msghdr *mh, int level, int type, socklen_t length);
 
+/* Type-safe, dereferencing version of cmsg_find() */
+#define CMSG_FIND_DATA(mh, level, type, ctype) \
+        ({                                                            \
+                struct cmsghdr *_found;                               \
+                _found = cmsg_find(mh, level, type, CMSG_LEN(sizeof(ctype))); \
+                (ctype*) (_found ? CMSG_DATA(_found) : NULL);         \
+        })
+
 /*
  * Certain hardware address types (e.g Infiniband) do not fit into sll_addr
  * (8 bytes) and run over the structure. This macro returns the correct size that