From 4068579e1e098fa81d48db9ba4432ab664c58561 Mon Sep 17 00:00:00 2001 From: Tom Herbert Date: Fri, 2 May 2014 16:29:58 -0700 Subject: [PATCH] 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 Signed-off-by: David S. Miller --- net/ipv6/ip6_checksum.c | 18 +++++++----------- net/ipv6/udp.c | 33 +++++++++++++++++++++++++++++++-- 2 files changed, 38 insertions(+), 13 deletions(-) diff --git a/net/ipv6/ip6_checksum.c b/net/ipv6/ip6_checksum.c index c69fe37b8104..da26224a5993 100644 --- a/net/ipv6/ip6_checksum.c +++ b/net/ipv6/ip6_checksum.c @@ -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. - */ - 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); + /* 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). + */ + return skb_checksum_init_zero_check(skb, proto, uh->check, + ip6_compute_pseudo); } EXPORT_SYMBOL(udp6_csum_init); diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c index d8d6ca04bb9d..4fcd9bca950e 100644 --- a/net/ipv6/udp.c +++ b/net/ipv6/udp.c @@ -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) { - 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 @@ 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; -- 2.39.5