swrap: Correctly update the msg_name in recvmsg()

This has been found while debugging nsupdate.

Signed-off-by: Andreas Schneider <asn@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>

diff --git a/lib/socket_wrapper/socket_wrapper.c b/lib/socket_wrapper/socket_wrapper.c
index 1188c4e538892088b01ec1c1bea728314b6a6765..bd2798bae55f38db0d9a4b10fc0c4e164ddcb861 100644 (file)
--- a/lib/socket_wrapper/socket_wrapper.c
+++ b/lib/socket_wrapper/socket_wrapper.c
@@ -4051,6 +4051,19 @@ static int swrap_recvmsg_after(int fd,
                avail += msg->msg_iov[i].iov_len;
        }
 
+       /* Convert the socket address before we leave */
+       if (si->type == SOCK_DGRAM && un_addr != NULL) {
+               rc = sockaddr_convert_from_un(si,
+                                             un_addr,
+                                             un_addrlen,
+                                             si->family,
+                                             msg->msg_name,
+                                             &msg->msg_namelen);
+               if (rc == -1) {
+                       goto done;
+               }
+       }
+
        if (avail == 0) {
                rc = 0;
                goto done;
@@ -4096,16 +4109,6 @@ static int swrap_recvmsg_after(int fd,
                }
 
                if (un_addr != NULL) {
-                       rc = sockaddr_convert_from_un(si,
-                                                     un_addr,
-                                                     un_addrlen,
-                                                     si->family,
-                                                     msg->msg_name,
-                                                     &msg->msg_namelen);
-                       if (rc == -1) {
-                               goto done;
-                       }
-
                        swrap_pcap_dump_packet(si,
                                          msg->msg_name,
                                          SWRAP_RECVFROM,
@@ -4549,9 +4552,6 @@ static ssize_t swrap_recvmsg(int s, struct msghdr *omsg, int flags)
 
        ret = libc_recvmsg(s, &msg, flags);
 
-       msg.msg_name = omsg->msg_name;
-       msg.msg_namelen = omsg->msg_namelen;
-
 #ifdef HAVE_STRUCT_MSGHDR_MSG_CONTROL
        msg_ctrllen_filled += msg.msg_controllen;
        msg_ctrllen_left -= msg.msg_controllen;
@@ -4593,6 +4593,23 @@ static ssize_t swrap_recvmsg(int s, struct msghdr *omsg, int flags)
 #endif
        omsg->msg_iovlen = msg.msg_iovlen;
 
+       /*
+        * From the manpage:
+        *
+        * The  msg_name  field  points  to a caller-allocated buffer that is
+        * used to return the source address if the socket is unconnected.  The
+        * caller should set msg_namelen to the size of this buffer before this
+        * call; upon return from a successful call, msg_name will contain the
+        * length of the returned address.  If the application  does  not  need
+        * to know the source address, msg_name can be specified as NULL.
+        */
+       if (omsg->msg_name != NULL &&
+           omsg->msg_namelen != 0 &&
+           omsg->msg_namelen >= msg.msg_namelen) {
+               memcpy(omsg->msg_name, msg.msg_name, msg.msg_namelen);
+               omsg->msg_namelen = msg.msg_namelen;
+       }
+
        return ret;
 }