netfilter: nf_nat: add nf_nat_csum()

Add a static function nf_nat_csum() to replace the duplicate code in
nf_nat_mangle_udp_packet() and __nf_nat_mangle_tcp_packet().

Signed-off-by: Changli Gao <xiaosuo@gmail.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>

1 files changed, 31 insertions, 45 deletions

diff --git a/net/ipv4/netfilter/nf_nat_helper.c b/net/ipv4/netfilter/nf_nat_helper.c
index 4a0c6b548eee..31427fb57aa8 100644
--- a/net/ipv4/netfilter/nf_nat_helper.c
+++ b/net/ipv4/netfilter/nf_nat_helper.c
@@ -153,6 +153,35 @@ void nf_nat_set_seq_adjust(struct nf_conn *ct, enum ip_conntrack_info ctinfo,
 }
 EXPORT_SYMBOL_GPL(nf_nat_set_seq_adjust);
 
+static void nf_nat_csum(struct sk_buff *skb, struct iphdr *iph, void *data,
+                        int datalen, __sum16 *check, int oldlen)
+{
+        struct rtable *rt = skb_rtable(skb);
+
+        if (skb->ip_summed != CHECKSUM_PARTIAL) {
+                if (!(rt->rt_flags & RTCF_LOCAL) &&
+                    skb->dev->features & NETIF_F_V4_CSUM) {
+                        skb->ip_summed = CHECKSUM_PARTIAL;
+                        skb->csum_start = skb_headroom(skb) +
+                                          skb_network_offset(skb) +
+                                          iph->ihl * 4;
+                        skb->csum_offset = (void *)check - data;
+                        *check = ~csum_tcpudp_magic(iph->saddr, iph->daddr,
+                                                    datalen, iph->protocol, 0);
+                } else {
+                        *check = 0;
+                        *check = csum_tcpudp_magic(iph->saddr, iph->daddr,
+                                                   datalen, iph->protocol,
+                                                   csum_partial(data, datalen,
+                                                                0));
+                        if (iph->protocol == IPPROTO_UDP && !*check)
+                                *check = CSUM_MANGLED_0;
+                }
+        } else
+                inet_proto_csum_replace2(check, skb,
+                                         htons(oldlen), htons(datalen), 1);
+}
+
 /* Generic function for mangling variable-length address changes inside
  * NATed TCP connections (like the PORT XXX,XXX,XXX,XXX,XXX,XXX
  * command in FTP).
@@ -169,7 +198,6 @@ int __nf_nat_mangle_tcp_packet(struct sk_buff *skb,
                                const char *rep_buffer,
                                unsigned int rep_len, bool adjust)
 {
-        struct rtable *rt = skb_rtable(skb);
         struct iphdr *iph;
         struct tcphdr *tcph;
         int oldlen, datalen;
@@ -192,26 +220,7 @@ int __nf_nat_mangle_tcp_packet(struct sk_buff *skb,
                         match_offset, match_len, rep_buffer, rep_len);
 
         datalen = skb->len - iph->ihl*4;
-        if (skb->ip_summed != CHECKSUM_PARTIAL) {
-                if (!(rt->rt_flags & RTCF_LOCAL) &&
-                    skb->dev->features & NETIF_F_V4_CSUM) {
-                        skb->ip_summed = CHECKSUM_PARTIAL;
-                        skb->csum_start = skb_headroom(skb) +
-                                          skb_network_offset(skb) +
-                                          iph->ihl * 4;
-                        skb->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(tcph,
-                                                                datalen, 0));
-                }
-        } else
-                inet_proto_csum_replace2(&tcph->check, skb,
-                                         htons(oldlen), htons(datalen), 1);
+        nf_nat_csum(skb, iph, tcph, datalen, &tcph->check, oldlen);
 
         if (adjust && rep_len != match_len)
                 nf_nat_set_seq_adjust(ct, ctinfo, tcph->seq,
@@ -240,7 +249,6 @@ nf_nat_mangle_udp_packet(struct sk_buff *skb,
                          const char *rep_buffer,
                          unsigned int rep_len)
 {
-        struct rtable *rt = skb_rtable(skb);
         struct iphdr *iph;
         struct udphdr *udph;
         int datalen, oldlen;
@@ -274,29 +282,7 @@ nf_nat_mangle_udp_packet(struct sk_buff *skb,
         if (!udph->check && skb->ip_summed != CHECKSUM_PARTIAL)
                 return 1;
 
-        if (skb->ip_summed != CHECKSUM_PARTIAL) {
-                if (!(rt->rt_flags & RTCF_LOCAL) &&
-                    skb->dev->features & NETIF_F_V4_CSUM) {
-                        skb->ip_summed = CHECKSUM_PARTIAL;
-                        skb->csum_start = skb_headroom(skb) +
-                                          skb_network_offset(skb) +
-                                          iph->ihl * 4;
-                        skb->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(udph,
-                                                                     datalen, 0));
-                        if (!udph->check)
-                                udph->check = CSUM_MANGLED_0;
-                }
-        } else
-                inet_proto_csum_replace2(&udph->check, skb,
-                                         htons(oldlen), htons(datalen), 1);
+        nf_nat_csum(skb, iph, udph, datalen, &udph->check, oldlen);
 
         return 1;
 }