karlseguin.tngl.sh
A websocket implementation for zig
client: poll for read readiness instead of SO_RCVTIMEO
The TLS read path goes through std.crypto.tls, whose reader treats a socket
EAGAIN (produced by SO_RCVTIMEO on timeout) as a programmer bug and panics in
debug builds. Poll the fd for readiness instead, so a read timeout surfaces as
error.WouldBlock without ever issuing a read that can EAGAIN.
author
Kyle 🐆
date
(Jun 17, 2026, 5:33 PM -0400)
commit
ae78dced
ae78dced086d70f6f09496e1b0f08ff7e201885f
parent
6d309f7a
6d309f7a9790030f2fc070323b5defc64a15c13b
+23
-3
+23
-3
src/client/client.zig
+23
-3
src/client/client.zig
···
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return self.stream.writeTimeout(ms);
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}
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-
pub fn readTimeout(self: *const Client, ms: u32) !void {
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+
pub fn readTimeout(self: *Client, ms: u32) !void {
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return self.stream.readTimeout(ms);
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}
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···
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io: Io,
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stream: Io.net.Stream,
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tls_client: ?*TLSClient = null,
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read_timeout_ms: u32 = 0,
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pub fn init(io: Io, stream: Io.net.Stream, tls_client: ?*TLSClient) Stream {
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return .{
···
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}
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pub fn read(self: *Stream, buf: []u8) !usize {
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// A read timeout is implemented by polling the socket for readiness
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// rather than SO_RCVTIMEO. On the TLS path the underlying read goes
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// through std.crypto.tls, whose reader treats a socket EAGAIN (what
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// SO_RCVTIMEO produces on timeout) as a programmer bug and panics in
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// debug builds. Polling lets a timeout surface as error.WouldBlock (which
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// read() turns into "no message") without ever issuing a read that could
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// EAGAIN. The caller drains its buffer before reaching here, so polling
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// only gates an actual socket read.
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if (self.read_timeout_ms > 0) {
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var pfd = [_]std.posix.pollfd{.{
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.fd = self.stream.socket.handle,
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.events = std.posix.POLL.IN,
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.revents = 0,
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}};
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const ready = std.posix.poll(&pfd, @intCast(self.read_timeout_ms)) catch 0;
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if (ready == 0) return error.WouldBlock;
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}
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if (self.tls_client) |tls_client| {
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var w: std.Io.Writer = .fixed(buf);
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while (true) {
···
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return self.setTimeout(posix.SO.SNDTIMEO, ms);
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}
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-
pub fn readTimeout(self: *const Stream, ms: u32) !void {
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-
return self.setTimeout(posix.SO.RCVTIMEO, ms);
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pub fn readTimeout(self: *Stream, ms: u32) !void {
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// Stored and applied via poll() in read(); see the note there for why this
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// does not use SO_RCVTIMEO.
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self.read_timeout_ms = ms;
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}
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fn setTimeout(self: *const Stream, opt_name: u32, ms: u32) !void {