[PATCH v2 net-next] net/sctp: Refactor SCTP skb checksum computation

[Joe Stringer <joe@xxxxxxxxxxx>]

This patch consolidates the SCTP checksum calculation code from various
places to a single new function, sctp_compute_cksum(skb, offset).

Signed-off-by: Joe Stringer <joe@xxxxxxxxxxx>
---
v2:
* Use skb->data + offset for start position of checksum calculation
* Fix existing bug in sctp_csum_check() where the incorrect offset was used
* Remove redundant variable in sctp_nat_csum()
---
 include/net/sctp/checksum.h           |   15 +++++++++++++++
 net/netfilter/ipvs/ip_vs_proto_sctp.c |   23 +++--------------------
 net/netfilter/nf_nat_proto_sctp.c     |    8 +-------
 net/sctp/input.c                      |   10 +---------
 4 files changed, 20 insertions(+), 36 deletions(-)

diff --git a/include/net/sctp/checksum.h b/include/net/sctp/checksum.h
index 0cb08e6..5d55082 100644
--- a/include/net/sctp/checksum.h
+++ b/include/net/sctp/checksum.h
@@ -85,4 +85,19 @@ static inline __le32 sctp_end_cksum(__u32 crc32)
        return cpu_to_le32(~crc32);
 }
 
+/* Calculate the CRC32C checksum of an SCTP packet.  */
+static inline __le32 sctp_compute_cksum(const struct sk_buff *skb,
+                                       unsigned int offset)
+{
+       const struct sk_buff *iter;
+
+       __u32 crc32 = sctp_start_cksum(skb->data + offset,
+                                      skb_headlen(skb) - offset);
+       skb_walk_frags(skb, iter)
+               crc32 = sctp_update_cksum((__u8 *) iter->data,
+                                         skb_headlen(iter), crc32);
+
+       return sctp_end_cksum(crc32);
+}
+
 #endif /* __sctp_checksum_h__ */
diff --git a/net/netfilter/ipvs/ip_vs_proto_sctp.c 
b/net/netfilter/ipvs/ip_vs_proto_sctp.c
index 3c0da87..23e596e 100644
--- a/net/netfilter/ipvs/ip_vs_proto_sctp.c
+++ b/net/netfilter/ipvs/ip_vs_proto_sctp.c
@@ -66,15 +66,7 @@ sctp_conn_schedule(int af, struct sk_buff *skb, struct 
ip_vs_proto_data *pd,
 static void sctp_nat_csum(struct sk_buff *skb, sctp_sctphdr_t *sctph,
                          unsigned int sctphoff)
 {
-       __u32 crc32;
-       struct sk_buff *iter;
-
-       crc32 = sctp_start_cksum((__u8 *)sctph, skb_headlen(skb) - sctphoff);
-       skb_walk_frags(skb, iter)
-               crc32 = sctp_update_cksum((u8 *) iter->data,
-                                         skb_headlen(iter), crc32);
-       sctph->checksum = sctp_end_cksum(crc32);
-
+       sctph->checksum = sctp_compute_cksum(skb, sctphoff);
        skb->ip_summed = CHECKSUM_UNNECESSARY;
 }
 
@@ -151,10 +143,7 @@ sctp_csum_check(int af, struct sk_buff *skb, struct 
ip_vs_protocol *pp)
 {
        unsigned int sctphoff;
        struct sctphdr *sh, _sctph;
-       struct sk_buff *iter;
-       __le32 cmp;
-       __le32 val;
-       __u32 tmp;
+       __le32 cmp, val;
 
 #ifdef CONFIG_IP_VS_IPV6
        if (af == AF_INET6)
@@ -168,13 +157,7 @@ sctp_csum_check(int af, struct sk_buff *skb, struct 
ip_vs_protocol *pp)
                return 0;
 
        cmp = sh->checksum;
-
-       tmp = sctp_start_cksum((__u8 *) sh, skb_headlen(skb));
-       skb_walk_frags(skb, iter)
-               tmp = sctp_update_cksum((__u8 *) iter->data,
-                                       skb_headlen(iter), tmp);
-
-       val = sctp_end_cksum(tmp);
+       val = sctp_compute_cksum(skb, sctphoff);
 
        if (val != cmp) {
                /* CRC failure, dump it. */
diff --git a/net/netfilter/nf_nat_proto_sctp.c 
b/net/netfilter/nf_nat_proto_sctp.c
index 396e55d..754536f 100644
--- a/net/netfilter/nf_nat_proto_sctp.c
+++ b/net/netfilter/nf_nat_proto_sctp.c
@@ -34,9 +34,7 @@ sctp_manip_pkt(struct sk_buff *skb,
               const struct nf_conntrack_tuple *tuple,
               enum nf_nat_manip_type maniptype)
 {
-       struct sk_buff *frag;
        sctp_sctphdr_t *hdr;
-       __u32 crc32;
 
        if (!skb_make_writable(skb, hdroff + sizeof(*hdr)))
                return false;
@@ -51,11 +49,7 @@ sctp_manip_pkt(struct sk_buff *skb,
                hdr->dest = tuple->dst.u.sctp.port;
        }
 
-       crc32 = sctp_start_cksum((u8 *)hdr, skb_headlen(skb) - hdroff);
-       skb_walk_frags(skb, frag)
-               crc32 = sctp_update_cksum((u8 *)frag->data, skb_headlen(frag),
-                                         crc32);
-       hdr->checksum = sctp_end_cksum(crc32);
+       hdr->checksum = sctp_compute_cksum(skb, hdroff);
 
        return true;
 }
diff --git a/net/sctp/input.c b/net/sctp/input.c
index 3fa4d85..944f70e 100644
--- a/net/sctp/input.c
+++ b/net/sctp/input.c
@@ -87,15 +87,7 @@ static inline int sctp_rcv_checksum(struct net *net, struct 
sk_buff *skb)
 {
        struct sctphdr *sh = sctp_hdr(skb);
        __le32 cmp = sh->checksum;
-       struct sk_buff *list;
-       __le32 val;
-       __u32 tmp = sctp_start_cksum((__u8 *)sh, skb_headlen(skb));
-
-       skb_walk_frags(skb, list)
-               tmp = sctp_update_cksum((__u8 *)list->data, skb_headlen(list),
-                                       tmp);
-
-       val = sctp_end_cksum(tmp);
+       __le32 val = sctp_compute_cksum(skb, 0);
 
        if (val != cmp) {
                /* CRC failure, dump it. */
-- 
1.7.10.4

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