[NETFILTER]: Add partial checksum validation helper

Move the UDP-Lite conntrack checksum validation to a generic helper
similar to nf_checksum() and make it fall back to nf_checksum()
in case the full packet is to be checksummed and hardware checksums
are available. This is to be used by DCCP conntrack, which also
needs to verify partial checksums.

Signed-off-by: Patrick McHardy <kaber@trash.net>

4 files changed, 94 insertions, 40 deletions

diff --git a/include/linux/netfilter.h b/include/linux/netfilter.h
index 66bc52060fd6..e4c66593b5c6 100644
--- a/include/linux/netfilter.h
+++ b/include/linux/netfilter.h
@@ -234,6 +234,11 @@ struct nf_afinfo {
         unsigned short  family;
         __sum16         (*checksum)(struct sk_buff *skb, unsigned int hook,
                                     unsigned int dataoff, u_int8_t protocol);
+        __sum16         (*checksum_partial)(struct sk_buff *skb,
+                                            unsigned int hook,
+                                            unsigned int dataoff,
+                                            unsigned int len,
+                                            u_int8_t protocol);
         int             (*route)(struct dst_entry **dst, struct flowi *fl);
         void            (*saveroute)(const struct sk_buff *skb,
                                      struct nf_queue_entry *entry);
@@ -263,6 +268,23 @@ nf_checksum(struct sk_buff *skb, unsigned int hook, unsigned int dataoff,
         return csum;
 }
 
+static inline __sum16
+nf_checksum_partial(struct sk_buff *skb, unsigned int hook,
+                    unsigned int dataoff, unsigned int len,
+                    u_int8_t protocol, unsigned short family)
+{
+        const struct nf_afinfo *afinfo;
+        __sum16 csum = 0;
+
+        rcu_read_lock();
+        afinfo = nf_get_afinfo(family);
+        if (afinfo)
+                csum = afinfo->checksum_partial(skb, hook, dataoff, len,
+                                                protocol);
+        rcu_read_unlock();
+        return csum;
+}
+
 extern int nf_register_afinfo(const struct nf_afinfo *afinfo);
 extern void nf_unregister_afinfo(const struct nf_afinfo *afinfo);
 
diff --git a/net/ipv4/netfilter.c b/net/ipv4/netfilter.c
index 9a904c6c0dc8..f8edacdf991d 100644
--- a/net/ipv4/netfilter.c
+++ b/net/ipv4/netfilter.c
@@ -182,21 +182,44 @@ __sum16 nf_ip_checksum(struct sk_buff *skb, unsigned int hook,
         }
         return csum;
 }
-
 EXPORT_SYMBOL(nf_ip_checksum);
 
+static __sum16 nf_ip_checksum_partial(struct sk_buff *skb, unsigned int hook,
+                                      unsigned int dataoff, unsigned int len,
+                                      u_int8_t protocol)
+{
+        const struct iphdr *iph = ip_hdr(skb);
+        __sum16 csum = 0;
+
+        switch (skb->ip_summed) {
+        case CHECKSUM_COMPLETE:
+                if (len == skb->len - dataoff)
+                        return nf_ip_checksum(skb, hook, dataoff, protocol);
+                /* fall through */
+        case CHECKSUM_NONE:
+                skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, protocol,
+                                               skb->len - dataoff, 0);
+                skb->ip_summed = CHECKSUM_NONE;
+                csum = __skb_checksum_complete_head(skb, dataoff + len);
+                if (!csum)
+                        skb->ip_summed = CHECKSUM_UNNECESSARY;
+        }
+        return csum;
+}
+
 static int nf_ip_route(struct dst_entry **dst, struct flowi *fl)
 {
         return ip_route_output_key(&init_net, (struct rtable **)dst, fl);
 }
 
 static const struct nf_afinfo nf_ip_afinfo = {
-        .family         = AF_INET,
-        .checksum       = nf_ip_checksum,
-        .route          = nf_ip_route,
-        .saveroute      = nf_ip_saveroute,
-        .reroute        = nf_ip_reroute,
-        .route_key_size = sizeof(struct ip_rt_info),
+        .family                 = AF_INET,
+        .checksum               = nf_ip_checksum,
+        .checksum_partial       = nf_ip_checksum_partial,
+        .route                  = nf_ip_route,
+        .saveroute              = nf_ip_saveroute,
+        .reroute                = nf_ip_reroute,
+        .route_key_size         = sizeof(struct ip_rt_info),
 };
 
 static int ipv4_netfilter_init(void)
diff --git a/net/ipv6/netfilter.c b/net/ipv6/netfilter.c
index aed51bcc66b4..8c6c5e71f210 100644
--- a/net/ipv6/netfilter.c
+++ b/net/ipv6/netfilter.c
@@ -121,16 +121,44 @@ __sum16 nf_ip6_checksum(struct sk_buff *skb, unsigned int hook,
         }
         return csum;
 }
-
 EXPORT_SYMBOL(nf_ip6_checksum);
 
+static __sum16 nf_ip6_checksum_partial(struct sk_buff *skb, unsigned int hook,
+                                       unsigned int dataoff, unsigned int len,
+                                       u_int8_t protocol)
+{
+        struct ipv6hdr *ip6h = ipv6_hdr(skb);
+        __wsum hsum;
+        __sum16 csum = 0;
+
+        switch (skb->ip_summed) {
+        case CHECKSUM_COMPLETE:
+                if (len == skb->len - dataoff)
+                        return nf_ip6_checksum(skb, hook, dataoff, protocol);
+                /* fall through */
+        case CHECKSUM_NONE:
+                hsum = skb_checksum(skb, 0, dataoff, 0);
+                skb->csum = ~csum_unfold(csum_ipv6_magic(&ip6h->saddr,
+                                                         &ip6h->daddr,
+                                                         skb->len - dataoff,
+                                                         protocol,
+                                                         csum_sub(0, hsum)));
+                skb->ip_summed = CHECKSUM_NONE;
+                csum = __skb_checksum_complete_head(skb, dataoff + len);
+                if (!csum)
+                        skb->ip_summed = CHECKSUM_UNNECESSARY;
+        }
+        return csum;
+};
+
 static const struct nf_afinfo nf_ip6_afinfo = {
-        .family         = AF_INET6,
-        .checksum       = nf_ip6_checksum,
-        .route          = nf_ip6_route,
-        .saveroute      = nf_ip6_saveroute,
-        .reroute        = nf_ip6_reroute,
-        .route_key_size = sizeof(struct ip6_rt_info),
+        .family                 = AF_INET6,
+        .checksum               = nf_ip6_checksum,
+        .checksum_partial       = nf_ip6_checksum_partial,
+        .route                  = nf_ip6_route,
+        .saveroute              = nf_ip6_saveroute,
+        .reroute                = nf_ip6_reroute,
+        .route_key_size         = sizeof(struct ip6_rt_info),
 };
 
 int __init ipv6_netfilter_init(void)
diff --git a/net/netfilter/nf_conntrack_proto_udplite.c b/net/netfilter/nf_conntrack_proto_udplite.c
index 9dd03c7aeac6..c3eaee6afffd 100644
--- a/net/netfilter/nf_conntrack_proto_udplite.c
+++ b/net/netfilter/nf_conntrack_proto_udplite.c
@@ -127,32 +127,13 @@ static int udplite_error(struct sk_buff *skb, unsigned int dataoff,
         }
 
         /* Checksum invalid? Ignore. */
-        if (nf_conntrack_checksum && !skb_csum_unnecessary(skb) &&
-            hooknum == NF_INET_PRE_ROUTING) {
-                if (pf == PF_INET) {
-                        struct iphdr *iph = ip_hdr(skb);
-
-                        skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr,
-                                                       udplen, IPPROTO_UDPLITE, 0);
-                } else {
-                        struct ipv6hdr *ipv6h = ipv6_hdr(skb);
-                        __wsum hsum = skb_checksum(skb, 0, dataoff, 0);
-
-                        skb->csum = ~csum_unfold(
-                                csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
-                                                udplen, IPPROTO_UDPLITE,
-                                                csum_sub(0, hsum)));
-                }
-
-                skb->ip_summed = CHECKSUM_NONE;
-                if (__skb_checksum_complete_head(skb, dataoff + cscov)) {
-                        if (LOG_INVALID(IPPROTO_UDPLITE))
-                                nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
-                                              "nf_ct_udplite: bad UDPLite "
-                                              "checksum ");
-                        return -NF_ACCEPT;
-                }
-                skb->ip_summed = CHECKSUM_UNNECESSARY;
+        if (nf_conntrack_checksum && hooknum == NF_INET_PRE_ROUTING &&
+            nf_checksum_partial(skb, hooknum, dataoff, cscov, IPPROTO_UDP,
+                                pf)) {
+                if (LOG_INVALID(IPPROTO_UDPLITE))
+                        nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
+                                      "nf_ct_udplite: bad UDPLite checksum ");
+                return -NF_ACCEPT;
         }
 
         return NF_ACCEPT;