[NETFILTER]: replace open coded checksum updates

Replace open coded checksum update by nf_csum_update calls and clean up
the surrounding code a bit.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 20 insertions, 33 deletions

diff --git a/net/ipv4/netfilter/ipt_ECN.c b/net/ipv4/netfilter/ipt_ECN.c
index 35916c74fe4e..7e30e6d2b5da 100644
--- a/net/ipv4/netfilter/ipt_ECN.c
+++ b/net/ipv4/netfilter/ipt_ECN.c
@@ -27,22 +27,18 @@ MODULE_DESCRIPTION("iptables ECN modification module");
 static inline int
 set_ect_ip(struct sk_buff **pskb, const struct ipt_ECN_info *einfo)
 {
-        if (((*pskb)->nh.iph->tos & IPT_ECN_IP_MASK)
-            != (einfo->ip_ect & IPT_ECN_IP_MASK)) {
-                u_int16_t diffs[2];
+        struct iphdr *iph = (*pskb)->nh.iph;
+        u_int16_t oldtos;
 
+        if ((iph->tos & IPT_ECN_IP_MASK) != (einfo->ip_ect & IPT_ECN_IP_MASK)) {
                 if (!skb_make_writable(pskb, sizeof(struct iphdr)))
                         return 0;
-
-                diffs[0] = htons((*pskb)->nh.iph->tos) ^ 0xFFFF;
-                (*pskb)->nh.iph->tos &= ~IPT_ECN_IP_MASK;
-                (*pskb)->nh.iph->tos |= (einfo->ip_ect & IPT_ECN_IP_MASK);
-                diffs[1] = htons((*pskb)->nh.iph->tos);
-                (*pskb)->nh.iph->check
-                        = csum_fold(csum_partial((char *)diffs,
-                                                 sizeof(diffs),
-                                                 (*pskb)->nh.iph->check
-                                                 ^0xFFFF));
+                iph = (*pskb)->nh.iph;
+                oldtos = iph->tos;
+                iph->tos &= ~IPT_ECN_IP_MASK;
+                iph->tos |= (einfo->ip_ect & IPT_ECN_IP_MASK);
+                iph->check = nf_csum_update(oldtos ^ 0xFFFF, iph->tos,
+                                            iph->check);
         } 
         return 1;
 }
diff --git a/net/ipv4/netfilter/ipt_TOS.c b/net/ipv4/netfilter/ipt_TOS.c
index 1c7a5ca399b3..52e9d705d48e 100644
--- a/net/ipv4/netfilter/ipt_TOS.c
+++ b/net/ipv4/netfilter/ipt_TOS.c
@@ -30,23 +30,17 @@ target(struct sk_buff **pskb,
        void *userinfo)
 {
         const struct ipt_tos_target_info *tosinfo = targinfo;
+        struct iphdr *iph = (*pskb)->nh.iph;
+        u_int16_t oldtos;
 
-        if (((*pskb)->nh.iph->tos & IPTOS_TOS_MASK) != tosinfo->tos) {
-                u_int16_t diffs[2];
-
+        if ((iph->tos & IPTOS_TOS_MASK) != tosinfo->tos) {
                 if (!skb_make_writable(pskb, sizeof(struct iphdr)))
                         return NF_DROP;
-
-                diffs[0] = htons((*pskb)->nh.iph->tos) ^ 0xFFFF;
-                (*pskb)->nh.iph->tos
-                        = ((*pskb)->nh.iph->tos & IPTOS_PREC_MASK)
-                        | tosinfo->tos;
-                diffs[1] = htons((*pskb)->nh.iph->tos);
-                (*pskb)->nh.iph->check
-                        = csum_fold(csum_partial((char *)diffs,
-                                                 sizeof(diffs),
-                                                 (*pskb)->nh.iph->check
-                                                 ^0xFFFF));
+                iph = (*pskb)->nh.iph;
+                oldtos = iph->tos;
+                iph->tos = (iph->tos & IPTOS_PREC_MASK) | tosinfo->tos;
+                iph->check = nf_csum_update(oldtos ^ 0xFFFF, iph->tos,
+                                            iph->check);
         }
         return IPT_CONTINUE;
 }
diff --git a/net/ipv4/netfilter/ipt_TTL.c b/net/ipv4/netfilter/ipt_TTL.c
index f48892ae0be5..2afb2a8aa8c5 100644
--- a/net/ipv4/netfilter/ipt_TTL.c
+++ b/net/ipv4/netfilter/ipt_TTL.c
@@ -27,7 +27,6 @@ ipt_ttl_target(struct sk_buff **pskb,
 {
         struct iphdr *iph;
         const struct ipt_TTL_info *info = targinfo;
-        u_int16_t diffs[2];
         int new_ttl;
 
         if (!skb_make_writable(pskb, (*pskb)->len))
@@ -55,12 +54,10 @@ ipt_ttl_target(struct sk_buff **pskb,
         }
 
         if (new_ttl != iph->ttl) {
-                diffs[0] = htons(((unsigned)iph->ttl) << 8) ^ 0xFFFF;
+                iph->check = nf_csum_update((iph->ttl << 8) ^ 0xFFFF,
+                                            new_ttl << 8,
+                                            iph->check);
                 iph->ttl = new_ttl;
-                diffs[1] = htons(((unsigned)iph->ttl) << 8);
-                iph->check = csum_fold(csum_partial((char *)diffs,
-                                                    sizeof(diffs),
-                                                    iph->check^0xFFFF));
         }
 
         return IPT_CONTINUE;