[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>

6 files changed, 40 insertions, 42 deletions

diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index 175e093ec564..e3eceecd0496 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -934,11 +934,11 @@ int icmp_rcv(struct sk_buff *skb)
         case CHECKSUM_HW:
                 if (!(u16)csum_fold(skb->csum))
                         break;
-                LIMIT_NETDEBUG(KERN_DEBUG "icmp v4 hw csum failure\n");
+                /* fall through */
         case CHECKSUM_NONE:
-                if ((u16)csum_fold(skb_checksum(skb, 0, skb->len, 0)))
+                skb->csum = 0;
+                if (__skb_checksum_complete(skb))
                         goto error;
-        default:;
         }
 
         if (!pskb_pull(skb, sizeof(struct icmphdr)))
diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index c6247fc84060..c04607b49212 100644
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -872,11 +872,18 @@ int igmp_rcv(struct sk_buff *skb)
                 return 0;
         }
 
-        if (!pskb_may_pull(skb, sizeof(struct igmphdr)) || 
-            (u16)csum_fold(skb_checksum(skb, 0, len, 0))) {
-                in_dev_put(in_dev);
-                kfree_skb(skb);
-                return 0;
+        if (!pskb_may_pull(skb, sizeof(struct igmphdr)))
+                goto drop;
+
+        switch (skb->ip_summed) {
+        case CHECKSUM_HW:
+                if (!(u16)csum_fold(skb->csum))
+                        break;
+                /* fall through */
+        case CHECKSUM_NONE:
+                skb->csum = 0;
+                if (__skb_checksum_complete(skb))
+                        goto drop;
         }
 
         ih = skb->h.igmph;
@@ -906,6 +913,8 @@ int igmp_rcv(struct sk_buff *skb)
         default:
                 NETDEBUG(KERN_DEBUG "New IGMP type=%d, why we do not know about it?\n", ih->type);
         }
+
+drop:
         in_dev_put(in_dev);
         kfree_skb(skb);
         return 0;
diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index 896ce3f8f53a..4e9c74b54b15 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -577,15 +577,16 @@ static int ipgre_rcv(struct sk_buff *skb)
                         goto drop_nolock;
 
                 if (flags&GRE_CSUM) {
-                        if (skb->ip_summed == CHECKSUM_HW) {
+                        switch (skb->ip_summed) {
+                        case CHECKSUM_HW:
                                 csum = (u16)csum_fold(skb->csum);
-                                if (csum)
-                                        skb->ip_summed = CHECKSUM_NONE;
-                        }
-                        if (skb->ip_summed == CHECKSUM_NONE) {
-                                skb->csum = skb_checksum(skb, 0, skb->len, 0);
+                                if (!csum)
+                                        break;
+                                /* fall through */
+                        case CHECKSUM_NONE:
+                                skb->csum = 0;
+                                csum = __skb_checksum_complete(skb);
                                 skb->ip_summed = CHECKSUM_HW;
-                                csum = (u16)csum_fold(skb->csum);
                         }
                         offset += 4;
                 }
diff --git a/net/ipv4/netfilter/ip_conntrack_proto_icmp.c b/net/ipv4/netfilter/ip_conntrack_proto_icmp.c
index 5198f3a1e2cd..e4d6b268e8c4 100644
--- a/net/ipv4/netfilter/ip_conntrack_proto_icmp.c
+++ b/net/ipv4/netfilter/ip_conntrack_proto_icmp.c
@@ -13,6 +13,7 @@
 #include <linux/in.h>
 #include <linux/icmp.h>
 #include <linux/seq_file.h>
+#include <linux/skbuff.h>
 #include <net/ip.h>
 #include <net/checksum.h>
 #include <linux/netfilter.h>
@@ -230,19 +231,15 @@ icmp_error(struct sk_buff *skb, enum ip_conntrack_info *ctinfo,
         case CHECKSUM_HW:
                 if (!(u16)csum_fold(skb->csum)) 
                         break;
-                if (LOG_INVALID(IPPROTO_ICMP))
-                        nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
-                                      "ip_ct_icmp: bad HW ICMP checksum ");
-                return -NF_ACCEPT;
+                /* fall through */
         case CHECKSUM_NONE:
-                if ((u16)csum_fold(skb_checksum(skb, 0, skb->len, 0))) {
+                skb->csum = 0;
+                if (__skb_checksum_complete(skb)) {
                         if (LOG_INVALID(IPPROTO_ICMP))
                                 nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
                                               "ip_ct_icmp: bad ICMP checksum ");
                         return -NF_ACCEPT;
                 }
-        default:
-                break;
         }
 
 checksum_skipped:
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 634dabb558fd..ac1fcf5b4ebc 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1110,24 +1110,18 @@ static struct sock *tcp_v4_hnd_req(struct sock *sk, struct sk_buff *skb)
 static int tcp_v4_checksum_init(struct sk_buff *skb)
 {
         if (skb->ip_summed == CHECKSUM_HW) {
-                skb->ip_summed = CHECKSUM_UNNECESSARY;
                 if (!tcp_v4_check(skb->h.th, skb->len, skb->nh.iph->saddr,
-                                  skb->nh.iph->daddr, skb->csum))
+                                  skb->nh.iph->daddr, skb->csum)) {
+                        skb->ip_summed = CHECKSUM_UNNECESSARY;
                         return 0;
-
-                LIMIT_NETDEBUG(KERN_DEBUG "hw tcp v4 csum failed\n");
-                skb->ip_summed = CHECKSUM_NONE;
+                }
         }
+
+        skb->csum = csum_tcpudp_nofold(skb->nh.iph->saddr, skb->nh.iph->daddr,
+                                       skb->len, IPPROTO_TCP, 0);
+
         if (skb->len <= 76) {
-                if (tcp_v4_check(skb->h.th, skb->len, skb->nh.iph->saddr,
-                                 skb->nh.iph->daddr,
-                                 skb_checksum(skb, 0, skb->len, 0)))
-                        return -1;
-                skb->ip_summed = CHECKSUM_UNNECESSARY;
-        } else {
-                skb->csum = ~tcp_v4_check(skb->h.th, skb->len,
-                                          skb->nh.iph->saddr,
-                                          skb->nh.iph->daddr, 0);
+                return __skb_checksum_complete(skb);
         }
         return 0;
 }
@@ -1219,7 +1213,7 @@ int tcp_v4_rcv(struct sk_buff *skb)
          * provided case of th->doff==0 is elimineted.
          * So, we defer the checks. */
         if ((skb->ip_summed != CHECKSUM_UNNECESSARY &&
-             tcp_v4_checksum_init(skb) < 0))
+             tcp_v4_checksum_init(skb)))
                 goto bad_packet;
 
         th = skb->h.th;
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index e0bd1013cb0d..2422a5f7195d 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -761,7 +761,7 @@ int udp_ioctl(struct sock *sk, int cmd, unsigned long arg)
 
 static __inline__ int __udp_checksum_complete(struct sk_buff *skb)
 {
-        return (unsigned short)csum_fold(skb_checksum(skb, 0, skb->len, skb->csum));
+        return __skb_checksum_complete(skb);
 }
 
 static __inline__ int udp_checksum_complete(struct sk_buff *skb)
@@ -1100,11 +1100,8 @@ static int udp_checksum_init(struct sk_buff *skb, struct udphdr *uh,
         if (uh->check == 0) {
                 skb->ip_summed = CHECKSUM_UNNECESSARY;
         } else if (skb->ip_summed == CHECKSUM_HW) {
-                skb->ip_summed = CHECKSUM_UNNECESSARY;
                 if (!udp_check(uh, ulen, saddr, daddr, skb->csum))
-                        return 0;
-                LIMIT_NETDEBUG(KERN_DEBUG "udp v4 hw csum failure.\n");
-                skb->ip_summed = CHECKSUM_NONE;
+                        skb->ip_summed = CHECKSUM_UNNECESSARY;
         }
         if (skb->ip_summed != CHECKSUM_UNNECESSARY)
                 skb->csum = csum_tcpudp_nofold(saddr, daddr, ulen, IPPROTO_UDP, 0);