netfilter: xt_sctp: use WORD_ROUND macro to calculate length of multiple of 4 bytes

Use  WORD_ROUND to round an int up to the next multiple of 4.
Signed-off-by: Shan Wei <shanwei@cn.fujitsu.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>

net/netfilter/xt_sctp.c

@@ -3,6 +3,7 @@
 #include <linux/skbuff.h>
 #include <net/ip.h>
 #include <net/ipv6.h>
+#include <net/sctp/sctp.h>
 #include <linux/sctp.h>
 
 #include <linux/netfilter/x_tables.h>
@@ -67,7 +68,7 @@ match_packet(const struct sk_buff *skb,
 			 ++i, offset, sch->type, htons(sch->length),
 			 sch->flags);
 #endif
-		offset += (ntohs(sch->length) + 3) & ~3;
+		offset += WORD_ROUND(ntohs(sch->length));
 
 		pr_debug("skb->len: %d\toffset: %d\n", skb->len, offset);