[NETFILTER]: nf_nat: use HW checksumming when possible

When mangling packets forwarded to a HW checksumming capable device,
offload recalculation of the checksum instead of doing it in software.

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

1 files changed, 37 insertions, 12 deletions

diff --git a/net/ipv4/netfilter/nf_nat_helper.c b/net/ipv4/netfilter/nf_nat_helper.c
index 8a40fbe842b7..15b6e5ce3a04 100644
--- a/net/ipv4/netfilter/nf_nat_helper.c
+++ b/net/ipv4/netfilter/nf_nat_helper.c
@@ -153,6 +153,7 @@ nf_nat_mangle_tcp_packet(struct sk_buff **pskb,
                          const char *rep_buffer,
                          unsigned int rep_len)
 {
+        struct rtable *rt = (struct rtable *)(*pskb)->dst;
         struct iphdr *iph;
         struct tcphdr *tcph;
         int oldlen, datalen;
@@ -176,11 +177,22 @@ nf_nat_mangle_tcp_packet(struct sk_buff **pskb,
 
         datalen = (*pskb)->len - iph->ihl*4;
         if ((*pskb)->ip_summed != CHECKSUM_PARTIAL) {
-                tcph->check = 0;
-                tcph->check = tcp_v4_check(datalen,
-                                           iph->saddr, iph->daddr,
-                                           csum_partial((char *)tcph,
-                                                        datalen, 0));
+                if (!(rt->rt_flags & RTCF_LOCAL) &&
+                    (*pskb)->dev->features & NETIF_F_ALL_CSUM) {
+                        (*pskb)->ip_summed = CHECKSUM_PARTIAL;
+                        (*pskb)->csum_start = skb_headroom(*pskb) +
+                                              skb_network_offset(*pskb) +
+                                              iph->ihl * 4;
+                        (*pskb)->csum_offset = offsetof(struct tcphdr, check);
+                        tcph->check = ~tcp_v4_check(datalen,
+                                                    iph->saddr, iph->daddr, 0);
+                } else {
+                        tcph->check = 0;
+                        tcph->check = tcp_v4_check(datalen,
+                                                   iph->saddr, iph->daddr,
+                                                   csum_partial((char *)tcph,
+                                                                datalen, 0));
+                }
         } else
                 nf_proto_csum_replace2(&tcph->check, *pskb,
                                        htons(oldlen), htons(datalen), 1);
@@ -217,6 +229,7 @@ nf_nat_mangle_udp_packet(struct sk_buff **pskb,
                          const char *rep_buffer,
                          unsigned int rep_len)
 {
+        struct rtable *rt = (struct rtable *)(*pskb)->dst;
         struct iphdr *iph;
         struct udphdr *udph;
         int datalen, oldlen;
@@ -251,13 +264,25 @@ nf_nat_mangle_udp_packet(struct sk_buff **pskb,
                 return 1;
 
         if ((*pskb)->ip_summed != CHECKSUM_PARTIAL) {
-                udph->check = 0;
-                udph->check = csum_tcpudp_magic(iph->saddr, iph->daddr,
-                                                datalen, IPPROTO_UDP,
-                                                csum_partial((char *)udph,
-                                                             datalen, 0));
-                if (!udph->check)
-                        udph->check = CSUM_MANGLED_0;
+                if (!(rt->rt_flags & RTCF_LOCAL) &&
+                    (*pskb)->dev->features & NETIF_F_ALL_CSUM) {
+                        (*pskb)->ip_summed = CHECKSUM_PARTIAL;
+                        (*pskb)->csum_start = skb_headroom(*pskb) +
+                                              skb_network_offset(*pskb) +
+                                              iph->ihl * 4;
+                        (*pskb)->csum_offset = offsetof(struct udphdr, check);
+                        udph->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr,
+                                                         datalen, IPPROTO_UDP,
+                                                         0);
+                } else {
+                        udph->check = 0;
+                        udph->check = csum_tcpudp_magic(iph->saddr, iph->daddr,
+                                                        datalen, IPPROTO_UDP,
+                                                        csum_partial((char *)udph,
+                                                                     datalen, 0));
+                        if (!udph->check)
+                                udph->check = CSUM_MANGLED_0;
+                }
         } else
                 nf_proto_csum_replace2(&udph->check, *pskb,
                                        htons(oldlen), htons(datalen), 1);