netfilter: xtables: remove almost-unused xt_match_param.data member

This member is taking up a "long" per match, yet is only used by one
module out of the roughly 90 modules, ip6t_hbh. ip6t_hbh can be
restructured a little to accomodate for the lack of the .data member.
This variant uses checking the par->match address, which should avoid
having to add two extra functions, including calls, i.e.

(hbh_mt6: call hbhdst_mt6(skb, par, NEXTHDR_OPT),
dst_mt6: call hbhdst_mt6(skb, par, NEXTHDR_DEST))

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>

2 files changed, 6 insertions, 6 deletions

diff --git a/include/linux/netfilter/x_tables.h b/include/linux/netfilter/x_tables.h
index c68ff82366b6..cf91473624e1 100644
--- a/include/linux/netfilter/x_tables.h
+++ b/include/linux/netfilter/x_tables.h
@@ -315,9 +315,6 @@ struct xt_match {
         /* Set this to THIS_MODULE if you are a module, otherwise NULL */
         struct module *me;
 
-        /* Free to use by each match */
-        unsigned long data;
-
         const char *table;
         unsigned int matchsize;
 #ifdef CONFIG_COMPAT
diff --git a/net/ipv6/netfilter/ip6t_hbh.c b/net/ipv6/netfilter/ip6t_hbh.c
index cbe8dec9744b..82593c8bdc3e 100644
--- a/net/ipv6/netfilter/ip6t_hbh.c
+++ b/net/ipv6/netfilter/ip6t_hbh.c
@@ -41,6 +41,8 @@ MODULE_ALIAS("ip6t_dst");
  *      5       -> RTALERT 2 x x
  */
 
+static struct xt_match hbh_mt6_reg[] __read_mostly;
+
 static bool
 hbh_mt6(const struct sk_buff *skb, const struct xt_match_param *par)
 {
@@ -58,7 +60,9 @@ hbh_mt6(const struct sk_buff *skb, const struct xt_match_param *par)
         unsigned int optlen;
         int err;
 
-        err = ipv6_find_hdr(skb, &ptr, par->match->data, NULL);
+        err = ipv6_find_hdr(skb, &ptr,
+                            (par->match == &hbh_mt6_reg[0]) ?
+                            NEXTHDR_HOP : NEXTHDR_DEST, NULL);
         if (err < 0) {
                 if (err != -ENOENT)
                         *par->hotdrop = true;
@@ -179,13 +183,13 @@ static bool hbh_mt6_check(const struct xt_mtchk_param *par)
 
 static struct xt_match hbh_mt6_reg[] __read_mostly = {
         {
+                /* Note, hbh_mt6 relies on the order of hbh_mt6_reg */
                 .name           = "hbh",
                 .family         = NFPROTO_IPV6,
                 .match          = hbh_mt6,
                 .matchsize      = sizeof(struct ip6t_opts),
                 .checkentry     = hbh_mt6_check,
                 .me             = THIS_MODULE,
-                .data           = NEXTHDR_HOP,
         },
         {
                 .name           = "dst",
@@ -194,7 +198,6 @@ static struct xt_match hbh_mt6_reg[] __read_mostly = {
                 .matchsize      = sizeof(struct ip6t_opts),
                 .checkentry     = hbh_mt6_check,
                 .me             = THIS_MODULE,
-                .data           = NEXTHDR_DEST,
         },
 };