TCP keepalive was configured (SetKeepAlivePeriod) but never actually
enabled (SO_KEEPALIVE) on accepted client connections. Go 1.26's
SetKeepAlivePeriod only sets TCP_KEEPIDLE — it does not call
setsockopt(SO_KEEPALIVE, 1). Without SO_KEEPALIVE the kernel never
sends probe packets, so dead connections from sleeping mobile clients
linger until the idle timeout fires.
Replace SetKeepAlive + SetKeepAlivePeriod with net.KeepAliveConfig
(available since Go 1.24) for explicit per-socket control:
Idle: 30s (time before first probe)
Interval: 10s (between probes)
Count: 3 (failed probes to declare dead)
This detects dead connections in ~60s instead of relying on system
defaults (tcp_keepalive_intvl=75s, probes=9 → up to 11 minutes).
Increase the default idle timeout from 1 minute to 5 minutes.
MTProto clients send ping_delay_disconnect every ~60s, which resets
the idle timer. The previous 1-minute default created a race: if a
ping arrived even 1–2 seconds late the relay was killed. A 5-minute
window also survives typical mobile sleep periods (phone idle 2–5 min)
where the NAT mapping is still alive and the connection can resume
without reconnection.
Ref: #132
DPI bypass tools like ByeDPI fragment a single TLS record into multiple
records to evade censorship. This broke ReadClientHello because it
assumed the entire ClientHello arrives in one TLS record.
Add reassembleTLSHandshake that reads continuation records and
reconstructs a single TLS record before parsing and HMAC verification.
Per RFC 5246 Section 6.2.1, handshake messages may be fragmented
across multiple records — this is valid TLS behavior.
appolimp