[PATCH v2 net-next 04/11] udp/ipv6: prioritise the ip6 path over ip4 checks

[Pavel Begunkov <asml.silence@gmail.com>]

For AF_INET6 sockets we care the most about ipv6 but not ip4 mappings as
it's requires some extra hops anyway. Take AF_INET6 case from the address
parsing switch and add an explicit path for it. It removes some extra
ifs from the path and removes the switch overhead.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 net/ipv6/udp.c | 37 +++++++++++++++++--------------------
 1 file changed, 17 insertions(+), 20 deletions(-)

diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index d6aedd4dab25..78ce5fc53b59 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1357,30 +1357,27 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 
 	/* destination address check */
 	if (sin6) {
-		if (addr_len < offsetof(struct sockaddr, sa_data))
-			return -EINVAL;
+		if (addr_len < SIN6_LEN_RFC2133 || sin6->sin6_family != AF_INET6) {
+			if (addr_len < offsetof(struct sockaddr, sa_data))
+				return -EINVAL;
 
-		switch (sin6->sin6_family) {
-		case AF_INET6:
-			if (addr_len < SIN6_LEN_RFC2133)
+			switch (sin6->sin6_family) {
+			case AF_INET:
+				goto do_udp_sendmsg;
+			case AF_UNSPEC:
+				msg->msg_name = sin6 = NULL;
+				msg->msg_namelen = addr_len = 0;
+				goto no_daddr;
+			default:
 				return -EINVAL;
-			daddr = &sin6->sin6_addr;
-			if (ipv6_addr_any(daddr) &&
-			    ipv6_addr_v4mapped(&np->saddr))
-				ipv6_addr_set_v4mapped(htonl(INADDR_LOOPBACK),
-						       daddr);
-			break;
-		case AF_INET:
-			goto do_udp_sendmsg;
-		case AF_UNSPEC:
-			msg->msg_name = sin6 = NULL;
-			msg->msg_namelen = addr_len = 0;
-			daddr = NULL;
-			break;
-		default:
-			return -EINVAL;
+			}
 		}
+
+		daddr = &sin6->sin6_addr;
+		if (ipv6_addr_any(daddr) && ipv6_addr_v4mapped(&np->saddr))
+			ipv6_addr_set_v4mapped(htonl(INADDR_LOOPBACK), daddr);
 	} else {
+no_daddr:
 		if (sk->sk_state != TCP_ESTABLISHED)
 			return -EDESTADDRREQ;
 		daddr = &sk->sk_v6_daddr;
-- 
2.36.0