packages/net/shadowsocks-libev/README.md

Skip to [recipes](#recipes) for quick setup instructions

# components

`ss-local` provides SOCKS5 proxy with UDP associate support.

	 socks5                                     ss              plain
	--------> tcp:local_address:local_port ----> ss server -------> dest

`ss-redir`.  The REDIRECT and TPROXY part are to be provided by `ss-rules` script.  REDIRECT is for tcp traffic (`SO_ORIGINAL_DST` only supports TCP).  TPROXY is for udp messages, but it's only available in the PREROUTING chain and as such cannot proxy local out traffic.

	  plain             plain                                 ss              plain
	---------> REDIRECT ------> tcp:local_address:local_port ----> ss server -----> original dest

	  plain            plain                                 ss              plain
	---------> TPROXY -------> udp:local_address:local_port -----> ss server -----> original dest

`ss-tunnel` provides ssh `-L` local-forwarding-like tunnel.  Typically it's used to tunnel DNS traffic to the remote.

	  plain                                       ss               plain
	---------> tcp|udp:local_address:local_port ------> ss server -------> tunnel_address

`ss-server`, the "ss server" in the above diagram

# uci

Option names are the same as those used in json config files.  Check `validate_xxx` func definition of the [service script](files/shadowsocks-libev.init) and shadowsocks-libev's own documentation for supported options and expected value types.  A [sample config file](files/shadowsocks-libev.config) is also provided for reference.

Every section have a `disabled` option to temporarily turn off the component instance or component instances referring to it.

Section type `server` is for definition of remote shadowsocks servers.  They will be referred to from other component sections and as such should be named (as compared to anonymous section).

Section type `ss_local`, `ss_redir`, `ss_tunnel` are for specification of shadowsocks-libev components.  They share mostly a common set of options like `local_port`, `verbose`, `fast_open`, `timeout`, etc.

Plugin options should be specified in `server` section and will be inherited by other compoenents referring to it.

We can have multiple instances of component and `server` sections.  The relationship between them is many-to-one.  This will have the following implications

 - It's possible to have both `ss_local` and `ss_redir` referring to the same `server` definition
 - It's possible to have multiple instances of `ss_redir` listening on the same address:port with `reuse_port` enabled referring to the same or different `server` sections

`ss_rules` section is for configuring the behaviour of `ss-rules` script.  There can only exist at most one such section with the name also being `ss_rules`

	redir_tcp		name of ss_redir section with mode tcp_only or tcp_and_udp
	redir_udp		name of ss_redir section with mode udp_only or tcp_and_udp
	ifnames			only apply rules on packets from these ifnames

	--- for incoming packets having source address in

	src_ips_bypass		will bypass the redir chain
	src_ips_forward		will always go through the redir chain
	src_ips_checkdst	will continue to have their destination addresses checked

	--- otherwise, the default action can be specified with

	src_default		bypass, forward, [checkdst]

	--- if the previous check result is checkdst,
	--- then packets having destination address in

	dst_ips_bypass_file
	dst_ips_bypass		will bypass the redir chain
	dst_ips_forward_file
	dst_ips_forward		will go through the redir chain

	--- otherwise, the default action can be specified with

	dst_default		[bypass], forward

	--- for local out tcp packets, the default action can be specified with

	local_default		[bypass], forward, checkdst

ss-rules now uses nft set for storing addresses/networks.  Those set names are also part of the API and can be populated by other programs, e.g. dnsmasq with builtin nft set support.  Note that while nftables set supports storing cidr networks when `interval` flag is on, it rejects elements with overlaping intervals.

Extra nftables expressions can be specified with `nft_tcp_extra` and `nft_udp_extra` to apply ss_rules only to selected tcp/udp traffics.  E.g. `tcp dport { 80, 443 }`, `udp dport 53`, etc.

# incompatible changes

| Commit date | Commit ID | Subject | Comment |
| ----------- | --------- | ------- | ------- |
| 2022-03-01  | fdaf2de2a | shadowsocks-libev: ss-rules: convert to using nft | ss-rules now uses nftables. UCI option ipt_args and dst_forward_recentrst are now deprecated and removed |
| 2020-08-03  | 7d7cbae75 | shadowsocks-libev: support ss-server option local_address_{v4,v6} | ss_server bind_address now deprecated, use local_address |
| 2019-05-09  | afe7d3424 | shadowsocks-libev: move plugin options to server section | This is a revision against c19e949 committed 2019-05-06 |
| 2017-07-02  | b61af9703 | shadowsocks-libev: rewrite | Packaging of shadowsocks-libev was rewritten from scratch |

# notes and faq

Useful paths and commands for debugging

	# check current running status
	ubus call service list '{"name": "shadowsocks-libev"}'
	ubus call service list '{"name": "shadowsocks-libev", "verbose": true}'

	# dump validate definition
	ubus call service validate '{"package": "shadowsocks-libev"}'
	ubus call service validate '{"package": "shadowsocks-libev"}' \
		| jsonfilter -e '$["shadowsocks-libev"]["ss_tunnel"]'

	# check json config
	ls -l /var/etc/shadowsocks-libev/

	# set uci config option verbose to 1, restart the service and follow the log
	logread -f

ss-redir needs to open a new socket and setsockopt IP_TRANSPARENT when sending udp reply to client.  This requires `CAP_NET_ADMIN` and as such the process cannot run as `nobody`

ss-local, ss-redir, etc. supports specifying an array of remote ss server, but supporting this in uci seems to be overkill.  The workaround can be defining multiple `server` sections and multiple `ss-redir` instances with `reuse_port` enabled

# recipes

## forward all

This will setup firewall rules to forward almost all incoming tcp/udp and locally generated tcp traffic (excluding those to private addresses like 192.168.0.0/16 etc.) through remote shadowsocks server

Install components.
Retry each command till it succeed

	opkg install shadowsocks-libev-ss-redir
	opkg install shadowsocks-libev-ss-rules
	opkg install shadowsocks-libev-ss-tunnel

Edit uci config `/etc/config/shadowsocks-libev`.
Replace `config server 'sss0'` section with parameters of your own remote shadowsocks server.
As for other options, change them only when you know the effect.

	config server 'sss0'
		option disabled 0
		option server '_sss_addr_'
		option server_port '_sss_port_'
		option password '********'
		option method 'aes-256-cfb'

	config ss_tunnel
		option disabled 0
		option server 'sss0'
		option local_address '0.0.0.0'
		option local_port '8053'
		option tunnel_address '8.8.8.8:53'
		option mode 'tcp_and_udp'

	config ss_redir ssr0
		option disabled 0
		option server 'sss0'
		option local_address '0.0.0.0'
		option local_port '1100'
		option mode 'tcp_and_udp'
		option reuse_port 1

	config ss_rules 'ss_rules'
		option disabled 0
		option redir_tcp 'ssr0'
		option redir_udp 'ssr0'
		option src_default 'checkdst'
		option dst_default 'forward'
		option local_default 'forward'

Restart shadowsocks-libev components

	/etc/init.d/shadowsocks-libev restart

Check if things are in place

	nft list ruleset | sed -r -n '/^\t[a-z]+ ss_rules[^ ]+ \{/,/^\t\}/p'
	netstat -lntp | grep -E '8053|1100'
	ps ww | grep ss-

Edit `/etc/config/dhcp`, making sure options are present in the first dnsmasq section like the following to let it use local tunnel endpoint for upstream dns query.
Option `noresolv` instructs dnsmasq to not use other dns servers like advertised by local isp.
Option `localuse` intends to make sure the device you are configuring also uses this dnsmasq instance as the resolver, not the ones from other sources.

	config dnsmasq
		...
		list server '127.0.0.1#8053'
		option noresolv 1
		option localuse 1

Restart dnsmasq

	/etc/init.d/dnsmasq restart

Check network on your computer

	nslookup www.google.com
	curl -vv https://www.google.com