src: introduce SYNPROXY matching

Add support for "synproxy" statement. For example (for TCP port 8888):

table ip x {
	chain y {
		type filter hook prerouting priority raw; policy accept;
		tcp dport 8888 tcp flags syn notrack
	}

	chain z {
		type filter hook input priority filter; policy accept;
		tcp dport 8888 ct state invalid,untracked synproxy mss 1460 wscale 7 timestamp sack-perm
		ct state invalid drop
	}
}

Signed-off-by: Fernando Fernandez Mancera <ffmancera@riseup.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 17 insertions, 0 deletions

diff --git a/src/netlink_linearize.c b/src/netlink_linearize.c
index 2c6aa64d..498326d0 100644
--- a/src/netlink_linearize.c
+++ b/src/netlink_linearize.c
@@ -1141,6 +1141,21 @@ static void netlink_gen_tproxy_stmt(struct netlink_linearize_ctx *ctx,
 	nftnl_rule_add_expr(ctx->nlr, nle);
 }
 
+static void netlink_gen_synproxy_stmt(struct netlink_linearize_ctx *ctx,
+				      const struct stmt *stmt)
+{
+	struct nftnl_expr *nle;
+
+	nle = alloc_nft_expr("synproxy");
+	nftnl_expr_set_u16(nle, NFTNL_EXPR_SYNPROXY_MSS, stmt->synproxy.mss);
+	nftnl_expr_set_u8(nle, NFTNL_EXPR_SYNPROXY_WSCALE,
+			  stmt->synproxy.wscale);
+	nftnl_expr_set_u32(nle, NFTNL_EXPR_SYNPROXY_FLAGS,
+			   stmt->synproxy.flags);
+
+	nftnl_rule_add_expr(ctx->nlr, nle);
+}
+
 static void netlink_gen_dup_stmt(struct netlink_linearize_ctx *ctx,
 				 const struct stmt *stmt)
 {
@@ -1382,6 +1397,8 @@ static void netlink_gen_stmt(struct netlink_linearize_ctx *ctx,
 		return netlink_gen_nat_stmt(ctx, stmt);
 	case STMT_TPROXY:
 		return netlink_gen_tproxy_stmt(ctx, stmt);
+	case STMT_SYNPROXY:
+		return netlink_gen_synproxy_stmt(ctx, stmt);
 	case STMT_DUP:
 		return netlink_gen_dup_stmt(ctx, stmt);
 	case STMT_QUEUE: