udp: Fix a memory leak in udp6_send()

[glebius]

Well, my comment says that I noticed the problem but wasn't sure enough to fix it :) The comment was added in a large unrelated change. Of course I have no objection.

[markj]

In D38993#889227, @glebius wrote:

Well, my comment says that I noticed the problem but wasn't sure enough to fix it :) The comment was added in a large unrelated change. Of course I have no objection.

FWIW, I wrote a test case for this and a related problem with v4-mapped addresses. I'll commit it soon.

sys/netinet6/udp6_usrreq.c

if ((inp->inp_flags & IN6P_IPV6_V6ONLY) == 0) {
                 }
         } else
 #endif
         if (sin6 && IN6_IS_ADDR_V4MAPPED(&sin6->sin6_addr)) {
                 /*
                  * Given this is either an IPv6-only socket or no INET is
                  * supported we will fail the send if the given destination
                  * address is a v4mapped address.
-                 *
-                 * XXXGL: do we leak m and control?
                  */
                 INP_UNLOCK(inp);
+                m_freem(m);
+                m_freem(control);
                 return (EINVAL);
         }
 
         NET_EPOCH_ENTER(et);
         if (control) {
                 if ((error = ip6_setpktopts(control, &opt,
                     inp->in6p_outputopts, td->td_ucred, nxt)) != 0) {
                         goto release;