[NETFILTER] ip6tables: remove duplicate code

Some IPv6 matches have very similar loops to find IPv6 extension header
and we can unify them. This patch introduces ipv6_find_hdr() to do it.
I just checked that it can find the target headers in the packet which has
dst,hbh,rt,frag,ah,esp headers.

Signed-off-by: Yasuyuki Kozakai <yasuyuki.kozakai@toshiba.co.jp>
Signed-off-by: Harald Welte <laforge@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 52 insertions, 0 deletions

diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index 1cb8adb2787..2da514b16d9 100644
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -1955,6 +1955,57 @@ static void __exit fini(void)
 #endif
 }
 
+/*
+ * find specified header up to transport protocol header.
+ * If found target header, the offset to the header is set to *offset
+ * and return 0. otherwise, return -1.
+ *
+ * Notes: - non-1st Fragment Header isn't skipped.
+ *        - ESP header isn't skipped.
+ *        - The target header may be trancated.
+ */
+int ipv6_find_hdr(const struct sk_buff *skb, unsigned int *offset, u8 target)
+{
+        unsigned int start = (u8*)(skb->nh.ipv6h + 1) - skb->data;
+        u8 nexthdr = skb->nh.ipv6h->nexthdr;
+        unsigned int len = skb->len - start;
+
+        while (nexthdr != target) {
+                struct ipv6_opt_hdr _hdr, *hp;
+                unsigned int hdrlen;
+
+                if ((!ipv6_ext_hdr(nexthdr)) || nexthdr == NEXTHDR_NONE)
+                        return -1;
+                hp = skb_header_pointer(skb, start, sizeof(_hdr), &_hdr);
+                if (hp == NULL)
+                        return -1;
+                if (nexthdr == NEXTHDR_FRAGMENT) {
+                        unsigned short _frag_off, *fp;
+                        fp = skb_header_pointer(skb,
+                                                start+offsetof(struct frag_hdr,
+                                                               frag_off),
+                                                sizeof(_frag_off),
+                                                &_frag_off);
+                        if (fp == NULL)
+                                return -1;
+
+                        if (ntohs(*fp) & ~0x7)
+                                return -1;
+                        hdrlen = 8;
+                } else if (nexthdr == NEXTHDR_AUTH)
+                        hdrlen = (hp->hdrlen + 2) << 2; 
+                else
+                        hdrlen = ipv6_optlen(hp); 
+
+                nexthdr = hp->nexthdr;
+                len -= hdrlen;
+                start += hdrlen;
+        }
+
+        *offset = start;
+        return 0;
+}
+
 EXPORT_SYMBOL(ip6t_register_table);
 EXPORT_SYMBOL(ip6t_unregister_table);
 EXPORT_SYMBOL(ip6t_do_table);
@@ -1963,6 +2014,7 @@ EXPORT_SYMBOL(ip6t_unregister_match);
 EXPORT_SYMBOL(ip6t_register_target);
 EXPORT_SYMBOL(ip6t_unregister_target);
 EXPORT_SYMBOL(ip6t_ext_hdr);
+EXPORT_SYMBOL(ipv6_find_hdr);
 
 module_init(init);
 module_exit(fini);