The 0.13 release line contains critical TCP correctness fixes that
backport into Red Bear:
- RFC 6298 retransmit backoff (was using a non-standard exponential
backoff with a different initial value)
- zero-window probes (the previous code did not implement them, so
connections stalled when the receiver advertised a 0 window)
- FIN retransmit in CLOSING state (the prior code only retransmitted
FIN from FIN-WAIT-1 and never recovered from a lost second FIN)
- SYN crash on unspecified address (the kernel would panic on a
SYN with src == 0.0.0.0; the 0.13.1 fix returns a RST)
- IPv6 SLAAC support on the wire when the upstream proto-ipv6
feature is enabled (Red Bear already enables proto-ipv6)
The code in scheme/ip.rs is already in 0.13.1 form (RawSocket::new
takes IpVersion directly, not Option<IpVersion>) and scheme/icmp.rs
already uses the 0.13.1 ip_protocol() signature, so the migration is
intentionally restricted to the version field. The Cargo.lock will be
regenerated by the canonical build (cookbook uses --locked, so the
next build-redbear.sh run will refresh the lockfile after the
workspace can resolve smoltcp 0.13.1).