ipv6 RAW: Disallow IPPROTO_IPV6-level IPV6_CHECKSUM socket option on ICMPv6 sockets.

RFC3542 tells that IPV6_CHECKSUM socket option in the IPPROTO_IPV6
level is not allowed on ICMPv6 sockets.  IPPROTO_RAW level
IPV6_CHECKSUM socket option (a Linux extension) is still allowed.
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/raw.c

@@ -971,6 +971,19 @@ static int do_rawv6_setsockopt(struct sock *sk, int level, int optname,
 
 	switch (optname) {
 		case IPV6_CHECKSUM:
+			if (inet_sk(sk)->num == IPPROTO_ICMPV6 &&
+			    level == IPPROTO_IPV6) {
+				/*
+				 * RFC3542 tells that IPV6_CHECKSUM socket
+				 * option in the IPPROTO_IPV6 level is not
+				 * allowed on ICMPv6 sockets.
+				 * If you want to set it, use IPPROTO_RAW
+				 * level IPV6_CHECKSUM socket option
+				 * (Linux extension).
+				 */
+				return -EINVAL;
+			}
+
 			/* You may get strange result with a positive odd offset;
 			   RFC2292bis agrees with me. */
 			if (val > 0 && (val&1))
@@ -1046,6 +1059,11 @@ static int do_rawv6_getsockopt(struct sock *sk, int level, int optname,
 
 	switch (optname) {
 	case IPV6_CHECKSUM:
+		/*
+		 * We allow getsockopt() for IPPROTO_IPV6-level
+		 * IPV6_CHECKSUM socket option on ICMPv6 sockets
+		 * since RFC3542 is silent about it.
+		 */
 		if (rp->checksum == 0)
 			val = -1;
 		else