Shadowsocks-libev dscp config ERROR on openwrt 23


I am using shadowsocks-libev v3.3.5 as a proxy for my openwrt router with this json configuration file:

  "server": <my_server_ip>,
  "server_port": 1090,
  "local_port": 8388,
  "password": "my_pass",
  "timeout": 86400,
  "method": "chacha20-ietf-poly1305",
  "reuse_port": true,
  "fast_open": false,
  "disable_sni": true,
  "mptcp": true,
  "dscp": {
    "8389": "CS1",
    "8390": "CS4"
  • I use dscp configuration for packets classification here

This was working fine on openwrt 21.02 (kernel version 5.4).

I upgraded my openwrt image to openwrt 23.05 (kernel version 5.15) and I started getting errors from shadowsocks binary about dscp configuration:

ERROR: setting ipv4 dscp failed: 22
ERROR: setting ipv6 dscp failed: 22

I tracked the error message in shadowsocks-libev source code in C and found that updating the socket options with the dscp value given in the configuration fails.
Here is the lines from redir.c file redir.c

    // Set non blocking

    if (listener->tos >= 0) {
        int rc = setsockopt(remotefd, IPPROTO_IP, IP_TOS, &listener->tos, sizeof(listener->tos));
        if (rc < 0 && errno != ENOPROTOOPT) {
            LOGE("setting ipv4 dscp failed: %d", errno);
        rc = setsockopt(remotefd, IPPROTO_IPV6, IPV6_TCLASS, &listener->tos, sizeof(listener->tos));
        if (rc < 0 && errno != ENOPROTOOPT) {
            LOGE("setting ipv6 dscp failed: %d", errno);

Did anyone face such an issue ?
Any idea about kernel updates/upgrades that shall cause this?

Thanks :slight_smile: