[NET]: Detect hardware rx checksum faults correctly

Here is the patch that introduces the generic skb_checksum_complete
which also checks for hardware RX checksum faults.  If that happens,
it'll call netdev_rx_csum_fault which currently prints out a stack
trace with the device name.  In future it can turn off RX checksum.

I've converted every spot under net/ that does RX checksum checks to
use skb_checksum_complete or __skb_checksum_complete with the
exceptions of:

* Those places where checksums are done bit by bit.  These will call
netdev_rx_csum_fault directly.

* The following have not been completely checked/converted:

ipmr
ip_vs
netfilter
dccp

This patch is based on patches and suggestions from Stephen Hemminger
and David S. Miller.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 44 insertions, 64 deletions

diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
index 23e540365a14..1bdf0fb8bf8a 100644
--- a/net/ipv6/icmp.c
+++ b/net/ipv6/icmp.c
@@ -585,17 +585,16 @@ static int icmpv6_rcv(struct sk_buff **pskb, unsigned int *nhoffp)
         daddr = &skb->nh.ipv6h->daddr;
 
         /* Perform checksum. */
-        if (skb->ip_summed == CHECKSUM_HW) {
-                skb->ip_summed = CHECKSUM_UNNECESSARY;
-                if (csum_ipv6_magic(saddr, daddr, skb->len, IPPROTO_ICMPV6,
-                                    skb->csum)) {
-                        LIMIT_NETDEBUG(KERN_DEBUG "ICMPv6 hw checksum failed\n");
-                        skb->ip_summed = CHECKSUM_NONE;
-                }
-        }
-        if (skb->ip_summed == CHECKSUM_NONE) {
-                if (csum_ipv6_magic(saddr, daddr, skb->len, IPPROTO_ICMPV6,
-                                    skb_checksum(skb, 0, skb->len, 0))) {
+        switch (skb->ip_summed) {
+        case CHECKSUM_HW:
+                if (!csum_ipv6_magic(saddr, daddr, skb->len, IPPROTO_ICMPV6,
+                                     skb->csum))
+                        break;
+                /* fall through */
+        case CHECKSUM_NONE:
+                skb->csum = ~csum_ipv6_magic(saddr, daddr, skb->len,
+                                             IPPROTO_ICMPV6, 0);
+                if (__skb_checksum_complete(skb)) {
                         LIMIT_NETDEBUG(KERN_DEBUG "ICMPv6 checksum failed [%04x:%04x:%04x:%04x:%04x:%04x:%04x:%04x > %04x:%04x:%04x:%04x:%04x:%04x:%04x:%04x]\n",
                                        NIP6(*saddr), NIP6(*daddr));
                         goto discard_it;
diff --git a/net/ipv6/raw.c b/net/ipv6/raw.c
index 651c79b41eeb..8e9628f1c4c5 100644
--- a/net/ipv6/raw.c
+++ b/net/ipv6/raw.c
@@ -298,13 +298,10 @@ void rawv6_err(struct sock *sk, struct sk_buff *skb,
 static inline int rawv6_rcv_skb(struct sock * sk, struct sk_buff * skb)
 {
         if ((raw6_sk(sk)->checksum || sk->sk_filter) && 
-            skb->ip_summed != CHECKSUM_UNNECESSARY) {
-                if ((unsigned short)csum_fold(skb_checksum(skb, 0, skb->len, skb->csum))) {
-                        /* FIXME: increment a raw6 drops counter here */
-                        kfree_skb(skb);
-                        return 0;
-                }
-                skb->ip_summed = CHECKSUM_UNNECESSARY;
+            skb_checksum_complete(skb)) {
+                /* FIXME: increment a raw6 drops counter here */
+                kfree_skb(skb);
+                return 0;
         }
 
         /* Charge it to the socket. */
@@ -337,32 +334,25 @@ int rawv6_rcv(struct sock *sk, struct sk_buff *skb)
         if (!rp->checksum)
                 skb->ip_summed = CHECKSUM_UNNECESSARY;
 
-        if (skb->ip_summed != CHECKSUM_UNNECESSARY) {
-                if (skb->ip_summed == CHECKSUM_HW) {
-                        skb_postpull_rcsum(skb, skb->nh.raw,
-                                           skb->h.raw - skb->nh.raw);
+        if (skb->ip_summed == CHECKSUM_HW) {
+                skb_postpull_rcsum(skb, skb->nh.raw,
+                                   skb->h.raw - skb->nh.raw);
+                if (!csum_ipv6_magic(&skb->nh.ipv6h->saddr,
+                                     &skb->nh.ipv6h->daddr,
+                                     skb->len, inet->num, skb->csum))
                         skb->ip_summed = CHECKSUM_UNNECESSARY;
-                        if (csum_ipv6_magic(&skb->nh.ipv6h->saddr,
-                                            &skb->nh.ipv6h->daddr,
-                                            skb->len, inet->num, skb->csum)) {
-                                LIMIT_NETDEBUG(KERN_DEBUG "raw v6 hw csum failure.\n");
-                                skb->ip_summed = CHECKSUM_NONE;
-                        }
-                }
-                if (skb->ip_summed == CHECKSUM_NONE)
-                        skb->csum = ~csum_ipv6_magic(&skb->nh.ipv6h->saddr,
-                                                     &skb->nh.ipv6h->daddr,
-                                                     skb->len, inet->num, 0);
         }
+        if (skb->ip_summed != CHECKSUM_UNNECESSARY)
+                skb->csum = ~csum_ipv6_magic(&skb->nh.ipv6h->saddr,
+                                             &skb->nh.ipv6h->daddr,
+                                             skb->len, inet->num, 0);
 
         if (inet->hdrincl) {
-                if (skb->ip_summed != CHECKSUM_UNNECESSARY &&
-                    (unsigned short)csum_fold(skb_checksum(skb, 0, skb->len, skb->csum))) {
+                if (skb_checksum_complete(skb)) {
                         /* FIXME: increment a raw6 drops counter here */
                         kfree_skb(skb);
                         return 0;
                 }
-                skb->ip_summed = CHECKSUM_UNNECESSARY;
         }
 
         rawv6_rcv_skb(sk, skb);
@@ -407,7 +397,7 @@ static int rawv6_recvmsg(struct kiocb *iocb, struct sock *sk,
         if (skb->ip_summed==CHECKSUM_UNNECESSARY) {
                 err = skb_copy_datagram_iovec(skb, 0, msg->msg_iov, copied);
         } else if (msg->msg_flags&MSG_TRUNC) {
-                if ((unsigned short)csum_fold(skb_checksum(skb, 0, skb->len, skb->csum)))
+                if (__skb_checksum_complete(skb))
                         goto csum_copy_err;
                 err = skb_copy_datagram_iovec(skb, 0, msg->msg_iov, copied);
         } else {
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index d746d3b27efb..62c0e5bd931c 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1401,20 +1401,18 @@ out:
 static int tcp_v6_checksum_init(struct sk_buff *skb)
 {
         if (skb->ip_summed == CHECKSUM_HW) {
-                skb->ip_summed = CHECKSUM_UNNECESSARY;
                 if (!tcp_v6_check(skb->h.th,skb->len,&skb->nh.ipv6h->saddr,
-                                  &skb->nh.ipv6h->daddr,skb->csum))
+                                  &skb->nh.ipv6h->daddr,skb->csum)) {
+                        skb->ip_summed = CHECKSUM_UNNECESSARY;
                         return 0;
-                LIMIT_NETDEBUG(KERN_DEBUG "hw tcp v6 csum failed\n");
+                }
         }
+
+        skb->csum = ~tcp_v6_check(skb->h.th,skb->len,&skb->nh.ipv6h->saddr,
+                                  &skb->nh.ipv6h->daddr, 0);
+
         if (skb->len <= 76) {
-                if (tcp_v6_check(skb->h.th,skb->len,&skb->nh.ipv6h->saddr,
-                                 &skb->nh.ipv6h->daddr,skb_checksum(skb, 0, skb->len, 0)))
-                        return -1;
-                skb->ip_summed = CHECKSUM_UNNECESSARY;
-        } else {
-                skb->csum = ~tcp_v6_check(skb->h.th,skb->len,&skb->nh.ipv6h->saddr,
-                                          &skb->nh.ipv6h->daddr,0);
+                return __skb_checksum_complete(skb);
         }
         return 0;
 }
@@ -1575,7 +1573,7 @@ static int tcp_v6_rcv(struct sk_buff **pskb, unsigned int *nhoffp)
                 goto discard_it;
 
         if ((skb->ip_summed != CHECKSUM_UNNECESSARY &&
-             tcp_v6_checksum_init(skb) < 0))
+             tcp_v6_checksum_init(skb)))
                 goto bad_packet;
 
         th = skb->h.th;
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index bf9519341fd3..e671153b47b2 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -248,7 +248,7 @@ try_again:
                 err = skb_copy_datagram_iovec(skb, sizeof(struct udphdr), msg->msg_iov,
                                               copied);
         } else if (msg->msg_flags&MSG_TRUNC) {
-                if ((unsigned short)csum_fold(skb_checksum(skb, 0, skb->len, skb->csum)))
+                if (__skb_checksum_complete(skb))
                         goto csum_copy_err;
                 err = skb_copy_datagram_iovec(skb, sizeof(struct udphdr), msg->msg_iov,
                                               copied);
@@ -363,13 +363,10 @@ static inline int udpv6_queue_rcv_skb(struct sock * sk, struct sk_buff *skb)
                 return -1;
         }
 
-        if (skb->ip_summed != CHECKSUM_UNNECESSARY) {
-                if ((unsigned short)csum_fold(skb_checksum(skb, 0, skb->len, skb->csum))) {
-                        UDP6_INC_STATS_BH(UDP_MIB_INERRORS);
-                        kfree_skb(skb);
-                        return 0;
-                }
-                skb->ip_summed = CHECKSUM_UNNECESSARY;
+        if (skb_checksum_complete(skb)) {
+                UDP6_INC_STATS_BH(UDP_MIB_INERRORS);
+                kfree_skb(skb);
+                return 0;
         }
 
         if (sock_queue_rcv_skb(sk,skb)<0) {
@@ -491,13 +488,10 @@ static int udpv6_rcv(struct sk_buff **pskb, unsigned int *nhoffp)
                 uh = skb->h.uh;
         }
 
-        if (skb->ip_summed==CHECKSUM_HW) {
+        if (skb->ip_summed == CHECKSUM_HW &&
+            !csum_ipv6_magic(saddr, daddr, ulen, IPPROTO_UDP, skb->csum))
                 skb->ip_summed = CHECKSUM_UNNECESSARY;
-                if (csum_ipv6_magic(saddr, daddr, ulen, IPPROTO_UDP, skb->csum)) {
-                        LIMIT_NETDEBUG(KERN_DEBUG "udp v6 hw csum failure.\n");
-                        skb->ip_summed = CHECKSUM_NONE;
-                }
-        }
+
         if (skb->ip_summed != CHECKSUM_UNNECESSARY)
                 skb->csum = ~csum_ipv6_magic(saddr, daddr, ulen, IPPROTO_UDP, 0);
 
@@ -521,8 +515,7 @@ static int udpv6_rcv(struct sk_buff **pskb, unsigned int *nhoffp)
                 if (!xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb))
                         goto discard;
 
-                if (skb->ip_summed != CHECKSUM_UNNECESSARY &&
-                    (unsigned short)csum_fold(skb_checksum(skb, 0, skb->len, skb->csum)))
+                if (skb_checksum_complete(skb))
                         goto discard;
                 UDP6_INC_STATS_BH(UDP_MIB_NOPORTS);