IPv6¶

tcpcc supports IPv6 on the public side while keeping the application backend on ordinary IPv4 loopback.

Direct CLI¶

Bracket the IPv6 literal:

sudo tcpcc \
  --forward '[2001:db8::10]:443=127.0.0.1:8443' \
  --cc bbr

version = 1
cc = "bbr"
memory_mib = 128

[[forward]]
listen = "[2001:db8::10]:443"
backend = "127.0.0.1:8443"

With an IPv6 public listener and no explicit TUN addresses, tcpcc uses:

host:   fd00:198:18::1
hosted: fd00:198:18::2

Explicit TUN addresses must also be IPv6 and the host/hosted addresses must differ.

IPv6 public routing requires:

sysctl net.ipv6.conf.all.forwarding

The expected value is 1.

This is intentional:

IPv6 public TCP
       ↓
hosted IPv6 TCP listener
       ↓
byte stream
       ↓
separate TCP connection
       ↓
127.0.0.1 backend

The backend application does not need to bind an IPv6 socket merely because the public endpoint is IPv6.

One tcpcc process cannot currently combine IPv4 and IPv6 public listeners. Run separate processes if the deployment requires both families.