sctp: deduplicate identical skb_checksum_ops

The same skb_checksum_ops struct is defined twice in two different places,
leading to code duplication. Declare it as a global variable into a common
header instead of allocating it on the stack on each function call.
bloat-o-meter reports a slight code shrink.

add/remove: 1/1 grow/shrink: 0/10 up/down: 128/-1282 (-1154)
Function                                     old     new   delta
sctp_csum_ops                                  -     128    +128
crc32c_csum_ops                               16       -     -16
sctp_rcv                                    6616    6583     -33
sctp_packet_pack                            4542    4504     -38
nf_conntrack_sctp_packet                    4980    4926     -54
execute_masked_set_action                   6453    6389     -64
tcf_csum_sctp                                575     428    -147
sctp_gso_segment                            1292    1126    -166
sctp_csum_check                              579     412    -167
sctp_snat_handler                            957     772    -185
sctp_dnat_handler                           1321    1132    -189
l4proto_manip_pkt                           2536    2313    -223
Total: Before=359297613, After=359296459, chg -0.00%
Reviewed-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Matteo Croce <mcroce@redhat.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/sctp/checksum.h

@@ -58,19 +58,21 @@ static inline __wsum sctp_csum_combine(__wsum csum, __wsum csum2,
 						   (__force __u32)csum2, len);
 }
 
+static const struct skb_checksum_ops sctp_csum_ops = {
+	.update  = sctp_csum_update,
+	.combine = sctp_csum_combine,
+};
+
 static inline __le32 sctp_compute_cksum(const struct sk_buff *skb,
 					unsigned int offset)
 {
 	struct sctphdr *sh = (struct sctphdr *)(skb->data + offset);
-	const struct skb_checksum_ops ops = {
-		.update  = sctp_csum_update,
-		.combine = sctp_csum_combine,
-	};
 	__le32 old = sh->checksum;
 	__wsum new;
 
 	sh->checksum = 0;
-	new = ~__skb_checksum(skb, offset, skb->len - offset, ~(__wsum)0, &ops);
+	new = ~__skb_checksum(skb, offset, skb->len - offset, ~(__wsum)0,
+			      &sctp_csum_ops);
 	sh->checksum = old;
 
 	return cpu_to_le32((__force __u32)new);

net/sctp/offload.c

@@ -103,11 +103,6 @@ static const struct net_offload sctp6_offload = {
 	},
 };
 
-static const struct skb_checksum_ops crc32c_csum_ops = {
-	.update  = sctp_csum_update,
-	.combine = sctp_csum_combine,
-};
-
 int __init sctp_offload_init(void)
 {
 	int ret;
@@ -120,7 +115,7 @@ int __init sctp_offload_init(void)
 	if (ret)
 		goto ipv4;
 
-	crc32c_csum_stub = &crc32c_csum_ops;
+	crc32c_csum_stub = &sctp_csum_ops;
 	return ret;
 
 ipv4: