[IPv6]: Change IPv6 unspecified destination address to ::1 for raw and un-connected sockets

This patch fixes a difference between IPv4 and IPv6 when sending packets
to the unspecified address (either 0.0.0.0 or ::) when using raw or
un-connected UDP sockets.  There are two cases where IPv6 either fails
to send anything, or sends with the destination address set to ::.  For
example:

--> ping -c1 0.0.0.0
PING 0.0.0.0 (127.0.0.1) 56(84) bytes of data.
64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=0.032 ms

--> ping6 -c1 ::
PING ::(::) 56 data bytes
ping: sendmsg: Invalid argument

Doing a sendto("0.0.0.0") reveals:

10:55:01.495090 IP localhost.32780 > localhost.7639: UDP, length 100

Doing a sendto("::") reveals:

10:56:13.262478 IP6 fe80::217:8ff:fe7d:4718.32779 > ::.7639: UDP, length 100

If you issue a connect() first in the UDP case, it will be sent to ::1,
similar to what happens with TCP.

This restores the BSD-ism.

Signed-off-by: Brian Haley <brian.haley@hp.com>
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>

net/ipv6/raw.c

@@ -805,15 +805,6 @@ static int rawv6_sendmsg(struct kiocb *iocb, struct sock *sk,
 		fl.fl6_flowlabel = np->flow_label;
 	}
 
-	if (ipv6_addr_any(daddr)) {
-		/*
-		 * unspecified destination address
-		 * treated as error... is this correct ?
-		 */
-		fl6_sock_release(flowlabel);
-		return(-EINVAL);
-	}
-
 	if (fl.oif == 0)
 		fl.oif = sk->sk_bound_dev_if;
 
@@ -846,7 +837,10 @@ static int rawv6_sendmsg(struct kiocb *iocb, struct sock *sk,
 	if (err)
 		goto out;
 
-	ipv6_addr_copy(&fl.fl6_dst, daddr);
+	if (!ipv6_addr_any(daddr))
+		ipv6_addr_copy(&fl.fl6_dst, daddr);
+	else
+		fl.fl6_dst.s6_addr[15] = 0x1; /* :: means loopback (BSD'ism) */
 	if (ipv6_addr_any(&fl.fl6_src) && !ipv6_addr_any(&np->saddr))
 		ipv6_addr_copy(&fl.fl6_src, &np->saddr);
 

net/ipv6/udp.c

@@ -752,7 +752,10 @@ do_udp_sendmsg:
 	opt = ipv6_fixup_options(&opt_space, opt);
 
 	fl.proto = sk->sk_protocol;
-	ipv6_addr_copy(&fl.fl6_dst, daddr);
+	if (!ipv6_addr_any(daddr))
+		ipv6_addr_copy(&fl.fl6_dst, daddr);
+	else
+		fl.fl6_dst.s6_addr[15] = 0x1; /* :: means loopback (BSD'ism) */
 	if (ipv6_addr_any(&fl.fl6_src) && !ipv6_addr_any(&np->saddr))
 		ipv6_addr_copy(&fl.fl6_src, &np->saddr);
 	fl.fl_ip_sport = inet->sport;