ipv4: Fix ip_getsockopt for IP_PKTOPTIONS

IP_PKTOPTIONS is broken for 32-bit applications running
in COMPAT mode on 64-bit kernels.

This happens because msghdr's msg_flags field is always
set to zero. When running in COMPAT mode this should be
set to MSG_CMSG_COMPAT instead.
Signed-off-by: Tiberiu Szocs-Mihai <tszocs@ixiacom.com>
Signed-off-by: Daniel Baluta <dbaluta@ixiacom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/ip_sockglue.c

@@ -1067,7 +1067,7 @@ EXPORT_SYMBOL(compat_ip_setsockopt);
  */
 
 static int do_ip_getsockopt(struct sock *sk, int level, int optname,
-			    char __user *optval, int __user *optlen)
+			    char __user *optval, int __user *optlen, unsigned flags)
 {
 	struct inet_sock *inet = inet_sk(sk);
 	int val;
@@ -1240,7 +1240,7 @@ static int do_ip_getsockopt(struct sock *sk, int level, int optname,
 
 		msg.msg_control = optval;
 		msg.msg_controllen = len;
-		msg.msg_flags = 0;
+		msg.msg_flags = flags;
 
 		if (inet->cmsg_flags & IP_CMSG_PKTINFO) {
 			struct in_pktinfo info;
@@ -1294,7 +1294,7 @@ int ip_getsockopt(struct sock *sk, int level,
 {
 	int err;
 
-	err = do_ip_getsockopt(sk, level, optname, optval, optlen);
+	err = do_ip_getsockopt(sk, level, optname, optval, optlen, 0);
 #ifdef CONFIG_NETFILTER
 	/* we need to exclude all possible ENOPROTOOPTs except default case */
 	if (err == -ENOPROTOOPT && optname != IP_PKTOPTIONS &&
@@ -1327,7 +1327,8 @@ int compat_ip_getsockopt(struct sock *sk, int level, int optname,
 		return compat_mc_getsockopt(sk, level, optname, optval, optlen,
 			ip_getsockopt);
 
-	err = do_ip_getsockopt(sk, level, optname, optval, optlen);
+	err = do_ip_getsockopt(sk, level, optname, optval, optlen,
+		MSG_CMSG_COMPAT);
 
 #ifdef CONFIG_NETFILTER
 	/* we need to exclude all possible ENOPROTOOPTs except default case */