shadowsocks-libev: ss-rules: new bool option --dst-forward-recentrst

Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>

net/shadowsocks-libev/Makefile

@@ -14,7 +14,7 @@ include $(TOPDIR)/rules.mk
 #
 PKG_NAME:=shadowsocks-libev
 PKG_VERSION:=3.0.8
-PKG_RELEASE:=7
+PKG_RELEASE:=8
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
 PKG_SOURCE_URL:=https://github.com/shadowsocks/shadowsocks-libev/releases/download/v$(PKG_VERSION)

net/shadowsocks-libev/README.md

@@ -67,9 +67,11 @@ We can have multiple instances of component and `server` sections.  The relation
 
 	local_default		[bypass], forward, checkdst
 
+Bool option `dst_forward_recentrst` requires iptables/netfilter `recent` match module (`opkg install iptables-mod-conntrack-extra`).  When enabled, `ss-rules` will setup iptables rules to forward through `ss-redir` those packets whose destination have recently sent to us multiple tcp-rst.
+
 ss-rules uses kernel ipset mechanism for storing addresses/networks.  Those ipsets are also part of the API and can be populated by other programs, e.g. dnsmasq with builtin ipset support.  For more details please read output of `ss-rules --help`
 
-Note also that `src_ips_xx` and `dst_ips_xx` actually also accepts cidr network representation.  Names are retained for backward compatibility coniderations
+Note also that `src_ips_xx` and `dst_ips_xx` actually also accepts cidr network representation.  Option names are retained in its current form for backward compatibility coniderations
 
 ## notes and faq
 

net/shadowsocks-libev/files/shadowsocks-libev.init

@@ -147,6 +147,7 @@ ss_rules() {
 	local bin="$ss_bindir/ss-rules"
 	local cfgtype
 	local local_port_tcp local_port_udp
+	local args
 
 	[ -x "$bin" ] || return 1
 	config_get cfgtype "$cfg" TYPE
@@ -160,6 +161,7 @@ ss_rules() {
 	eval local_port_udp="\$ss_rules_redir_udp_$redir_udp"
 	[ -n "$local_port_tcp" -o -n "$local_port_udp" ] || return 1
 	ss_redir_servers="$(echo "$ss_redir_servers" | tr ' ' '\n' | sort -u)"
+	[ "$dst_forward_recentrst" = 0 ] || args="$args --dst-forward-recentrst"
 
 	"$bin" \
 			-s "$ss_redir_servers" \
@@ -177,6 +179,7 @@ ss_rules() {
 			--src-checkdst "$src_ips_checkdst" \
 			--ifnames "$ifnames" \
 			--ipt-extra "$ipt_args" \
+			$args \
 		|| "$bin" -f
 }
 
@@ -294,6 +297,7 @@ validate_ss_rules_section() {
 		'src_default:or("bypass", "forward", "checkdst"):checkdst' \
 		'dst_default:or("bypass", "forward"):bypass' \
 		'local_default:or("bypass", "forward", "checkdst"):bypass' \
+		'dst_forward_recentrst:bool:0' \
 		'ifnames:list(maxlength(15))' \
 		'ipt_args:string'
 }

net/shadowsocks-libev/files/ss-rules

@@ -33,6 +33,9 @@ Usage: ss-rules [options]
 	--dst-forward-file <file>
 	--dst-default <bypass|forward>
 	                Same as with their --src-xx equivalent
+	--dst-forward-recentrst
+	                Forward those packets whose destinations have recently
+	                sent to us multiple tcp-rst packets
 	--local-default <bypass|forward|checkdst>
 	                Default action for local out TCP traffic
 
@@ -94,6 +97,7 @@ ss_rules_parse_args() {
 			--src-checkdst) o_src_checkdst="$2"; shift 2;;
 			--dst-bypass) o_dst_bypass="$2"; shift 2;;
 			--dst-forward) o_dst_forward="$2"; shift 2;;
+			--dst-forward-recentrst) o_dst_forward_recentrst=1; shift 1;;
 			--dst-bypass-file) o_dst_bypass_file="$2"; shift 2;;
 			--dst-forward-file) o_dst_forward_file="$2"; shift 2;;
 			*) __errmsg "unknown option $1"; return 1;;
@@ -104,6 +108,10 @@ ss_rules_parse_args() {
 		__errmsg "Requires at least -l or -L option"
 		return 1
 	fi
+	if [ -n "$o_dst_forward_recentrst" ] && ! iptables -m recent -h >/dev/null; then
+		__errmsg "Please install iptables-mod-conntrack-extra with opkg"
+		return 1
+	fi
 }
 
 ss_rules_flush() {
@@ -125,6 +133,7 @@ ss_rules_ipset_init() {
 		create ss_rules_dst_bypass hash:net hashsize 64
 		create ss_rules_dst_bypass_ hash:net hashsize 64
 		create ss_rules_dst_forward hash:net hashsize 64
+		create ss_rules_dst_forward_recentrst_ hash:ip hashsize 64 timeout 3600
 		$(ss_rules_ipset_mkadd ss_rules_dst_bypass_ "$o_dst_bypass_ $o_remote_servers")
 		$(ss_rules_ipset_mkadd ss_rules_src_bypass "$o_src_bypass")
 		$(ss_rules_ipset_mkadd ss_rules_src_forward "$o_src_forward")
@@ -151,8 +160,6 @@ ss_rules_iptchains_init() {
 ss_rules_iptchains_init_tcp() {
 	local ipt="iptables -t nat"
 	local local_target
-	local forward_rules
-	local r
 
 	[ -n "$o_redir_tcp_port" ] || return 0
 
@@ -184,10 +191,22 @@ ss_rules_iptchains_init_() {
 	local proto="$2"
 	local forward_rules
 	local src_default_target dst_default_target
+	local recentrst_mangle_rules recentrst_addset_rules
 
 	case "$proto" in
 		tcp)
 			forward_rules="-A ss_rules_forward -p tcp -j REDIRECT --to-ports $o_redir_tcp_port"
+			if [ -n "$o_dst_forward_recentrst" ]; then
+				recentrst_mangle_rules="
+					*mangle
+					-I PREROUTING 1 -p tcp -m tcp --tcp-flags RST RST -m recent --name ss_rules_recentrst --set --rsource
+					COMMIT
+				"
+				recentrst_addset_rules="
+					-A ss_rules_dst -m recent --name ss_rules_recentrst --rcheck --rdest --seconds 3 --hitcount 3 -j SET --add-set ss_rules_dst_forward_recentrst_ dst --exist
+					-A ss_rules_dst -m set --match-set ss_rules_dst_forward_recentrst_ dst -j ss_rules_forward
+				"
+			fi
 			;;
 		udp)
 			ip rule add fwmark 1 lookup 100
@@ -204,7 +223,7 @@ ss_rules_iptchains_init_() {
 		forward) dst_default_target=ss_rules_forward ;;
 		bypass|*) dst_default_target=RETURN ;;
 	esac
-	iptables-restore --noflush <<-EOF
+	sed -e '/^\s*$/d' -e 's/^\s\+//' <<-EOF | iptables-restore --noflush
 		*$table
 		:ss_rules_pre_src -
 		:ss_rules_src -
@@ -219,9 +238,11 @@ ss_rules_iptchains_init_() {
 		-A ss_rules_src -j $src_default_target -m comment --comment "src_default: $o_src_default"
 		-A ss_rules_dst -m set --match-set ss_rules_dst_bypass dst -j RETURN
 		-A ss_rules_dst -m set --match-set ss_rules_dst_forward dst -j ss_rules_forward
+		$recentrst_addset_rules
 		-A ss_rules_dst -j $dst_default_target -m comment --comment "dst_default: $o_dst_default"
 		$forward_rules
 		COMMIT
+		$recentrst_mangle_rules
 	EOF
 }