extensions: libxt_length: Add translation to nft

Add translation for module length to nftables.

Examples:

$ sudo iptables-translate -A INPUT -p icmp -m length --length 86:0xffff -j DROP
nft add rule ip filter INPUT ip protocol icmp meta length 86-65535 counter drop

$ sudo iptables-translate -A INPUT -p udp -m length --length :400
nft add rule ip filter INPUT ip protocol udp meta length 0-400 counter

$ sudo iptables-translate -A INPUT -p udp -m length --length 40
nft add rule ip filter INPUT ip protocol udp meta length 40 counter

$ sudo iptables-translate -A INPUT -p udp -m length ! --length 40
nft add rule ip filter INPUT ip protocol udp meta length != 40 counter

Signed-off-by: Shivani Bhardwaj <shivanib134@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/extensions/libxt_length.c b/extensions/libxt_length.c
index 6ea76465f858f642b44534bc966fae8a94724c11..96dab0cf434892da804cd47bed5646d24c96cdbd 100644 (file)
--- a/extensions/libxt_length.c
+++ b/extensions/libxt_length.c
@@ -56,6 +56,21 @@ static void length_save(const void *ip, const struct xt_entry_match *match)
                printf("%u:%u", info->min, info->max);
 }
 
+static int length_xlate(const struct xt_entry_match *match,
+                       struct xt_buf *buf, int numeric)
+{
+       const struct xt_length_info *info = (void *)match->data;
+
+       xt_buf_add(buf, "meta length %s", info->invert ? "!= " : "");
+       if (info->min == info->max)
+               xt_buf_add(buf, "%u ", info->min);
+       else
+               xt_buf_add(buf, "%u-%u ", info->min, info->max);
+
+       return 1;
+}
+
+
 static struct xtables_match length_match = {
        .family         = NFPROTO_UNSPEC,
        .name           = "length",
@@ -67,6 +82,7 @@ static struct xtables_match length_match = {
        .save           = length_save,
        .x6_parse       = length_parse,
        .x6_options     = length_opts,
+       .xlate          = length_xlate,
 };
 
 void _init(void)