net: Implmement RFC 6936 (zero RX csums for UDP/IPv6)
RFC 6936 relaxes the requirement of RFC 2460 that UDP/IPv6 packets which
are received with a zero UDP checksum value must be dropped. RFC 6936
allows zero checksums to support tunnels over UDP.
When sk_no_check is set we allow on a socket we allow a zero IPv6
UDP checksum. This is for both sending zero checksum and accepting
a zero checksum on receive.
Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index d8d6ca0..4fcd9bc 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -760,6 +760,17 @@
if (unlikely(skb1))
kfree_skb(skb1);
}
+
+static void udp6_csum_zero_error(struct sk_buff *skb)
+{
+ /* RFC 2460 section 8.1 says that we SHOULD log
+ * this error. Well, it is reasonable.
+ */
+ LIMIT_NETDEBUG(KERN_INFO "IPv6: udp checksum is 0 for [%pI6c]:%u->[%pI6c]:%u\n",
+ &ipv6_hdr(skb)->saddr, ntohs(udp_hdr(skb)->source),
+ &ipv6_hdr(skb)->daddr, ntohs(udp_hdr(skb)->dest));
+}
+
/*
* Note: called only from the BH handler context,
* so we don't need to lock the hashes.
@@ -779,7 +790,12 @@
dif = inet6_iif(skb);
sk = udp_v6_mcast_next(net, sk, uh->dest, daddr, uh->source, saddr, dif);
while (sk) {
- stack[count++] = sk;
+ /* If zero checksum and sk_no_check is not on for
+ * the socket then skip it.
+ */
+ if (uh->check || sk->sk_no_check)
+ stack[count++] = sk;
+
sk = udp_v6_mcast_next(net, sk_nulls_next(sk), uh->dest, daddr,
uh->source, saddr, dif);
if (unlikely(count == ARRAY_SIZE(stack))) {
@@ -867,6 +883,11 @@
if (sk != NULL) {
int ret;
+ if (!uh->check && !sk->sk_no_check) {
+ udp6_csum_zero_error(skb);
+ goto csum_error;
+ }
+
ret = udpv6_queue_rcv_skb(sk, skb);
sock_put(sk);
@@ -879,6 +900,11 @@
return 0;
}
+ if (!uh->check) {
+ udp6_csum_zero_error(skb);
+ goto csum_error;
+ }
+
if (!xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb))
goto discard;
@@ -1006,7 +1032,10 @@
if (is_udplite)
csum = udplite_csum_outgoing(sk, skb);
- else if (skb->ip_summed == CHECKSUM_PARTIAL) { /* UDP hardware csum */
+ else if (sk->sk_no_check == UDP_CSUM_NOXMIT) { /* UDP csum disabled */
+ skb->ip_summed = CHECKSUM_NONE;
+ goto send;
+ } else if (skb->ip_summed == CHECKSUM_PARTIAL) { /* UDP hardware csum */
udp6_hwcsum_outgoing(sk, skb, &fl6->saddr, &fl6->daddr,
up->len);
goto send;