Commit 4068579e authored by Tom Herbert's avatar Tom Herbert Committed by David S. Miller
Browse files

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: default avatarTom Herbert <therbert@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent e4f45b7f

net/ipv6/ip6_checksum.c

+7 −11
Original line number Diff line number Diff line
@@ -75,16 +75,12 @@ int udp6_csum_init(struct sk_buff *skb, struct udphdr *uh, int proto) 
			return err;

	}



	if (uh->check == 0) {

		/* RFC 2460 section 8.1 says that we SHOULD log

		   this error. Well, it is reasonable.

	/* To support RFC 6936 (allow zero checksum in UDP/IPV6 for tunnels)

	 * we accept a checksum of zero here. When we find the socket

	 * for the UDP packet we'll check if that socket allows zero checksum

	 * for IPv6 (set by socket option).

	 */

		LIMIT_NETDEBUG(KERN_INFO "IPv6: udp checksum is 0 for [%pI6c]:%u->[%pI6c]:%u\n",

			       &ipv6_hdr(skb)->saddr, ntohs(uh->source),

			       &ipv6_hdr(skb)->daddr, ntohs(uh->dest));

		return 1;

	}



	return skb_checksum_init(skb, IPPROTO_UDP, ip6_compute_pseudo);

	return skb_checksum_init_zero_check(skb, proto, uh->check,

					   ip6_compute_pseudo);

}

EXPORT_SYMBOL(udp6_csum_init);

net/ipv6/udp.c

+31 −2
Original line number Diff line number Diff line
@@ -760,6 +760,17 @@ static void flush_stack(struct sock **stack, unsigned int count, 
	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 @@ static int __udp6_lib_mcast_deliver(struct net *net, struct sk_buff *skb, 
	dif = inet6_iif(skb);

	sk = udp_v6_mcast_next(net, sk, uh->dest, daddr, uh->source, saddr, dif);

	while (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 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable, 
	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 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable, 
		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 @@ static int udp_v6_push_pending_frames(struct sock *sk) 


	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;

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