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Date: Fri, 4 Apr 2014 17:28:24 -0700 (PDT)
From: Tom Herbert <therbert@...gle.com>
To: davem@...emloft.net, netdev@...r.kernel.org
Subject: [PATCH net-next 6/6] 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
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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