mirror of
https://github.com/tailscale/tailscale.git
synced 2026-04-03 14:13:12 -04:00
2de38961af
Add server-side per-client bandwidth enforcement using TCP backpressure. When configured, the server calls WaitN after reading each non-DISCO data frame, which delays the next read, fills the TCP receive buffer, shrinks the TCP window, and naturally throttles the sender — no packets are dropped. Key design decisions: - Rate limiting is on the receive (inbound) side, which is what an abusive client controls - DISCO frames are exempt since they are small control messages critical for NAT traversal and direct connection establishment - Mesh peers are exempt since they are trusted infrastructure - The burst size is clamped to at least MaxPacketSize (64KB) to ensure a single max-size frame can always be processed - ServerInfo.TokenBucketBytesPerSecond/Burst are populated to inform clients of the server-side limit Also refactors sclient to store a context.Context directly instead of a done channel, which simplifies the rate limiter's WaitN call. Flags added to cmd/derper: --per-client-rate-limit (bytes/sec, default 0 = unlimited) --per-client-rate-burst (bytes, default 0 = 2x rate limit) Example for 10Mbps: --per-client-rate-limit=1250000 Updates #38509 Signed-off-by: Mike O'Driscoll <mikeo@tailscale.com>