[PATCH] extensions: libipt_REDIRECT: Add translation to nft

[Shivani Bhardwaj <shivanib134@gmail.com>]

Add translation for target REDIRECT to nftables.

Examples:

$ sudo iptables-translate -t nat -A prerouting -p tcp --dport 80 -j REDIRECT --to-ports 8080
nft add rule ip nat prerouting tcp dport 80 counter redirect to 8080

$ sudo iptables-translate -t nat -A prerouting -p tcp --dport 80 -j REDIRECT --to-ports 8080 --random
nft add rule ip nat prerouting tcp dport 80 counter redirect to 8080 random

Signed-off-by: Shivani Bhardwaj <shivanib134@gmail.com>
---
 extensions/libipt_REDIRECT.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/extensions/libipt_REDIRECT.c b/extensions/libipt_REDIRECT.c
index 610a949..2e5b33d 100644
--- a/extensions/libipt_REDIRECT.c
+++ b/extensions/libipt_REDIRECT.c
@@ -135,6 +135,24 @@ static void REDIRECT_save(const void *ip, const struct xt_entry_target *target)
 	}
 }
 
+static int REDIRECT_xlate(const struct xt_entry_target *target,
+			  struct xt_buf *buf, int numeric)
+{
+	const struct nf_nat_ipv4_multi_range_compat *mr =
+					(const void *)target->data;
+	const struct nf_nat_ipv4_range *r = &mr->range[0];
+
+	if (r->flags & NF_NAT_RANGE_PROTO_SPECIFIED) {
+		xt_buf_add(buf, "redirect to %hu", ntohs(r->min.tcp.port));
+		if (r->max.tcp.port != r->min.tcp.port)
+			xt_buf_add(buf, "-%hu ", ntohs(r->max.tcp.port));
+		if (mr->range[0].flags & NF_NAT_RANGE_PROTO_RANDOM)
+			xt_buf_add(buf, " random ");
+	}
+
+	return 1;
+}
+
 static struct xtables_target redirect_tg_reg = {
 	.name		= "REDIRECT",
 	.version	= XTABLES_VERSION,
@@ -147,6 +165,7 @@ static struct xtables_target redirect_tg_reg = {
 	.print		= REDIRECT_print,
 	.save		= REDIRECT_save,
 	.x6_options	= REDIRECT_opts,
+	.xlate		= REDIRECT_xlate,
 };
 
 void _init(void)
-- 
1.9.1