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Date: Sat, 5 Apr 2014 14:56:55 -0700
From: Tom Herbert <therbert@...gle.com>
To: David Miller <davem@...emloft.net>,
Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 6/6] net: Implmement RFC 6936 (zero RX csums for UDP/IPv6)
Please disregard new option, I think we can just use sk_no_check
instead of new socket option.
On Fri, Apr 4, 2014 at 5:28 PM, Tom Herbert <therbert@...gle.com> wrote:
> 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
> allow zero checksums to support tunnels over UDP.
>
> This patch adds a new socket option UDP_CHECK6_ZERO_OKAY whcih can be
> set on a UDP socket to indicate that a zero checksum is acceptable
> (e.g. the socket is for a tunnel). The ip6 checksum and UDP receive
> functions were updated accordingly to deal with this.
>
> Signed-off-by: Tom Herbert <therbert@...gle.com>
> ---
> include/linux/udp.h | 3 ++-
> include/uapi/linux/udp.h | 1 +
> net/ipv4/udp.c | 8 ++++++++
> net/ipv6/ip6_checksum.c | 19 ++++++++-----------
> net/ipv6/udp.c | 39 +++++++++++++++++++++++++++++++++++++--
> 5 files changed, 56 insertions(+), 14 deletions(-)
>
> diff --git a/include/linux/udp.h b/include/linux/udp.h
> index 42278bb..647ffc9 100644
> --- a/include/linux/udp.h
> +++ b/include/linux/udp.h
> @@ -63,7 +63,8 @@ struct udp_sock {
> #define UDPLITE_SEND_CC 0x2 /* set via udplite setsockopt */
> #define UDPLITE_RECV_CC 0x4 /* set via udplite setsocktopt */
> __u8 pcflag; /* marks socket as UDP-Lite if > 0 */
> - __u8 unused[3];
> + __u8 check6_zero_okay; /* Zero csum okay for IPv6 */
> + __u8 unused[2];
> /*
> * For encapsulation sockets.
> */
> diff --git a/include/uapi/linux/udp.h b/include/uapi/linux/udp.h
> index e2bcfd7..46d0e58 100644
> --- a/include/uapi/linux/udp.h
> +++ b/include/uapi/linux/udp.h
> @@ -28,6 +28,7 @@ struct udphdr {
>
> /* UDP socket options */
> #define UDP_CORK 1 /* Never send partially complete segments */
> +#define UDP_CHECK6_ZERO_OKAY 2 /* Zero checksum okay for IPv6 UDP */
> #define UDP_ENCAP 100 /* Set the socket to accept encapsulated packets */
>
> /* UDP encapsulation types */
> diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> index d5e3a76..9b88788 100644
> --- a/net/ipv4/udp.c
> +++ b/net/ipv4/udp.c
> @@ -2003,6 +2003,10 @@ int udp_lib_setsockopt(struct sock *sk, int level, int optname,
> }
> break;
>
> + case UDP_CHECK6_ZERO_OKAY:
> + up->check6_zero_okay = !!val;
> + break;
> +
> /*
> * UDP-Lite's partial checksum coverage (RFC 3828).
> */
> @@ -2081,6 +2085,10 @@ int udp_lib_getsockopt(struct sock *sk, int level, int optname,
> val = up->corkflag;
> break;
>
> + case UDP_CHECK6_ZERO_OKAY:
> + val = up->check6_zero_okay;
> + break;
> +
> case UDP_ENCAP:
> val = up->encap_type;
> break;
> diff --git a/net/ipv6/ip6_checksum.c b/net/ipv6/ip6_checksum.c
> index 6105b8f..55896cd 100644
> --- a/net/ipv6/ip6_checksum.c
> +++ b/net/ipv6/ip6_checksum.c
> @@ -83,16 +83,13 @@ 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_pseudo_compute);
> + /*
> + * 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_pseudo_compute);
> }
> EXPORT_SYMBOL(udp6_csum_init);
> diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
> index 1e586d9..8b874b9 100644
> --- a/net/ipv6/udp.c
> +++ b/net/ipv6/udp.c
> @@ -760,13 +760,25 @@ 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.
> */
> static int __udp6_lib_mcast_deliver(struct net *net, struct sk_buff *skb,
> const struct in6_addr *saddr, const struct in6_addr *daddr,
> - struct udp_table *udptable)
> + struct udp_table *udptable, int proto)
> {
> struct sock *sk, *stack[256 / sizeof(struct sock *)];
> const struct udphdr *uh = udp_hdr(skb);
> @@ -779,6 +791,19 @@ 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 (!uh->check && !udp_sk(sk)->check6_zero_okay) {
> + /*
> + * If checksum in packet is zero and not all the
> + * sockets accept a zero checksum then declare
> + * a checksum error.
> + */
> + flush_stack(stack, count, skb, ~0);
> + count = 0;
> + udp6_csum_zero_error(skb);
> + UDP6_INC_STATS_BH(net, UDP_MIB_CSUMERRORS, proto == IPPROTO_UDPLITE);
> + UDP6_INC_STATS_BH(net, UDP_MIB_INERRORS, proto == IPPROTO_UDPLITE);
> + break;
> + }
> stack[count++] = sk;
> sk = udp_v6_mcast_next(net, sk_nulls_next(sk), uh->dest, daddr,
> uh->source, saddr, dif);
> @@ -855,7 +880,7 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
> */
> if (ipv6_addr_is_multicast(daddr))
> return __udp6_lib_mcast_deliver(net, skb,
> - saddr, daddr, udptable);
> + saddr, daddr, udptable, proto);
>
> /* Unicast */
>
> @@ -867,6 +892,11 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
> if (sk != NULL) {
> int ret;
>
> + if (!uh->check && !udp_sk(sk)->check6_zero_okay) {
> + udp6_csum_zero_error(skb);
> + goto csum_error;
> + }
> +
> ret = udpv6_queue_rcv_skb(sk, skb);
> sock_put(sk);
>
> @@ -879,6 +909,11 @@ 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;
>
> --
> 1.9.1.423.g4596e3a
>
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