krb5 commit [krb5-1.15]: Use pktinfo for explicit UDP wildcard listeners

[Tom Yu]

https://github.com/krb5/krb5/commit/e23d062471bf9071072aaf2df39054508fe74cc1
commit e23d062471bf9071072aaf2df39054508fe74cc1
Author: Greg Hudson <ghudson at mit.edu>
Date:   Mon Dec 26 15:18:05 2016 -0500

    Use pktinfo for explicit UDP wildcard listeners
    
    In net-server.c, use pktinfo on UDP server sockets if they are bound
    to wildcard addresses, whether that is explicit or implicit in the
    address specification.
    
    (cherry picked from commit d005beaa72c70bc28b2b0b49b9d83eff160ca8f1)
    
    ticket: 8530
    version_fixed: 1.15.1

 src/lib/apputils/net-server.c |   13 ++++++++++++-
 1 files changed, 12 insertions(+), 1 deletions(-)

diff --git a/src/lib/apputils/net-server.c b/src/lib/apputils/net-server.c
index d64ffdd..29ec84a 100644
--- a/src/lib/apputils/net-server.c
+++ b/src/lib/apputils/net-server.c
@@ -105,6 +105,17 @@ paddr(struct sockaddr *sa)
     return buf;
 }
 
+/* Return true if sa is an IPv4 or IPv6 wildcard address. */
+static int
+is_wildcard(struct sockaddr *sa)
+{
+    if (sa->sa_family == AF_INET6)
+        return IN6_IS_ADDR_UNSPECIFIED(&sa2sin6(sa)->sin6_addr);
+    else if (sa->sa_family == AF_INET)
+        return sa2sin(sa)->sin_addr.s_addr == INADDR_ANY;
+    return 0;
+}
+
 /* KDC data.  */
 
 enum conn_type {
@@ -753,7 +764,7 @@ setup_socket(struct socksetup *data, struct bind_address *ba,
     }
 
     /* Try to turn on pktinfo for UDP wildcard sockets. */
-    if (ba->type == UDP && ba->address == NULL) {
+    if (ba->type == UDP && is_wildcard(sock_address)) {
         krb5_klog_syslog(LOG_DEBUG, _("Setting pktinfo on socket %s"),
                          paddr(sock_address));
         ret = set_pktinfo(sock, sock_address->sa_family);