From dd1c758c0ea81442f301843cfbe6a9bc8d138b2b Mon Sep 17 00:00:00 2001
From: Nikolay Govorov <me@govorov.online>
Date: Thu, 26 Feb 2026 07:51:47 +0000
Subject: [PATCH] Use common epoll for all net operations

---
 src/Net.zig         | 328 ++++++++++++++++++++++++++++++++++++++++++++
 src/Server.zig      |  63 ++++++---
 src/http/Client.zig |   8 ++
 src/sys/libcurl.zig |  42 ++++++
 4 files changed, 423 insertions(+), 18 deletions(-)

diff --git a/src/Net.zig b/src/Net.zig
index bd723be6..58070233 100644
--- a/src/Net.zig
+++ b/src/Net.zig
@@ -19,6 +19,7 @@
 const std = @import("std");
 const builtin = @import("builtin");
 const posix = std.posix;
+const linux = std.os.linux;
 const Allocator = std.mem.Allocator;
 const ArenaAllocator = std.heap.ArenaAllocator;
 const libcurl = @import("sys/libcurl.zig");
@@ -476,9 +477,17 @@ pub const Handles = struct {
     available: HandleList,
     multi: *libcurl.CurlM,
     performing: bool = false,
+    runtime_ctx: ?RuntimeContext = null,
 
     pub const HandleList = std.DoublyLinkedList;
 
+    const RuntimeContext = struct {
+        handles: *Handles,
+        runtime: *Runtime,
+        cdp_fd: ?posix.fd_t,
+        timer_deadline_ms: ?i64 = null,
+    };
+
     pub fn init(
         allocator: Allocator,
         ca_blob: ?libcurl.CurlBlob,
@@ -532,6 +541,9 @@ pub const Handles = struct {
 
     pub fn add(self: *Handles, conn: *const Connection) !void {
         try libcurl.curl_multi_add_handle(self.multi, conn.easy);
+        if (self.runtime_ctx != null) {
+            _ = try self.socketActionTimeout();
+        }
     }
 
     pub fn remove(self: *Handles, conn: *Connection) void {
@@ -554,6 +566,10 @@ pub const Handles = struct {
     }
 
     pub fn perform(self: *Handles) !c_int {
+        if (self.runtime_ctx != null) {
+            return self.socketActionTimeout();
+        }
+
         self.performing = true;
         defer self.performing = false;
 
@@ -579,6 +595,34 @@ pub const Handles = struct {
     }
 
     pub fn poll(self: *Handles, extra_fds: []libcurl.CurlWaitFd, timeout_ms: c_int) !void {
+        if (self.runtime_ctx) |*ctx| {
+            var wait_ms: i32 = @intCast(timeout_ms);
+            try self.runDueTimer();
+
+            if (ctx.timer_deadline_ms) |deadline| {
+                const now = std.time.milliTimestamp();
+                if (deadline > now) {
+                    const remaining: i32 = @intCast(@min(deadline - now, std.math.maxInt(i32)));
+                    wait_ms = @min(wait_ms, remaining);
+                } else {
+                    wait_ms = 0;
+                }
+            }
+
+            const watched_fd: ?posix.fd_t = if (extra_fds.len > 0) extra_fds[0].fd else ctx.cdp_fd;
+            const watched_ready = try ctx.runtime.dispatchFor(wait_ms, watched_fd);
+
+            if (extra_fds.len > 0) {
+                extra_fds[0].revents = .{};
+                if (watched_ready) {
+                    extra_fds[0].revents.pollin = true;
+                }
+            }
+
+            try self.runDueTimer();
+            return;
+        }
+
         try libcurl.curl_multi_poll(self.multi, extra_fds, timeout_ms, null);
     }
 
@@ -598,6 +642,128 @@ pub const Handles = struct {
             else => unreachable,
         };
     }
+
+    pub fn attachRuntime(self: *Handles, runtime: *Runtime, cdp_fd: ?posix.fd_t) !void {
+        self.detachRuntime();
+        self.runtime_ctx = .{
+            .handles = self,
+            .runtime = runtime,
+            .cdp_fd = cdp_fd,
+            .timer_deadline_ms = null,
+        };
+
+        const ctx = &self.runtime_ctx.?;
+        try libcurl.curl_multi_setopt(self.multi, .socket_function, onCurlSocket);
+        try libcurl.curl_multi_setopt(self.multi, .socket_data, ctx);
+        try libcurl.curl_multi_setopt(self.multi, .timer_function, onCurlTimer);
+        try libcurl.curl_multi_setopt(self.multi, .timer_data, ctx);
+        _ = try self.socketActionTimeout();
+    }
+
+    pub fn detachRuntime(self: *Handles) void {
+        if (self.runtime_ctx) |*ctx| {
+            ctx.runtime.removeByCtx(ctx);
+        }
+        libcurl.curl_multi_setopt(self.multi, .socket_function, @as(?*const libcurl.CurlSocketCallback, null)) catch {};
+        libcurl.curl_multi_setopt(self.multi, .socket_data, @as(?*anyopaque, null)) catch {};
+        libcurl.curl_multi_setopt(self.multi, .timer_function, @as(?*const libcurl.CurlTimerCallback, null)) catch {};
+        libcurl.curl_multi_setopt(self.multi, .timer_data, @as(?*anyopaque, null)) catch {};
+        self.runtime_ctx = null;
+    }
+
+    fn runDueTimer(self: *Handles) !void {
+        const ctx = &(self.runtime_ctx orelse return);
+        const deadline = ctx.timer_deadline_ms orelse return;
+        if (std.time.milliTimestamp() < deadline) {
+            return;
+        }
+        ctx.timer_deadline_ms = null;
+        _ = try self.socketActionTimeout();
+    }
+
+    fn socketAction(self: *Handles, fd: posix.fd_t, events: u32) !c_int {
+        const select_mask = runtimeEventsToCurlSelect(events).toC();
+        var running: c_int = undefined;
+        self.performing = true;
+        defer self.performing = false;
+        try libcurl.curl_multi_socket_action(self.multi, @intCast(fd), select_mask, &running);
+        return running;
+    }
+
+    fn socketActionTimeout(self: *Handles) !c_int {
+        var running: c_int = undefined;
+        self.performing = true;
+        defer self.performing = false;
+        try libcurl.curl_multi_socket_action(self.multi, libcurl.CURL_SOCKET_TIMEOUT, 0, &running);
+        return running;
+    }
+
+    fn runtimeEventsToCurlSelect(events: u32) libcurl.CurlSelectMask {
+        return .{
+            .in = (events & Runtime.READABLE) != 0,
+            .out = (events & Runtime.WRITABLE) != 0,
+            .err = (events & Runtime.ERROR) != 0,
+        };
+    }
+
+    fn curlPollToRuntimeEvents(what: libcurl.CurlPoll) u32 {
+        return switch (what) {
+            .in => Runtime.READABLE | Runtime.ERROR,
+            .out => Runtime.WRITABLE | Runtime.ERROR,
+            .inout => Runtime.READABLE | Runtime.WRITABLE | Runtime.ERROR,
+            .remove => 0,
+        };
+    }
+
+    fn onRuntimeFdEvent(ctx_ptr: *anyopaque, event: RuntimeEvent) anyerror!void {
+        const ctx: *RuntimeContext = @ptrCast(@alignCast(ctx_ptr));
+        _ = try ctx.handles.socketAction(event.fd, event.events);
+    }
+
+    fn onCurlSocket(
+        easy: ?*libcurl.Curl,
+        s: libcurl.CurlSocket,
+        what_raw: c_int,
+        userp: ?*anyopaque,
+        socketp: ?*anyopaque,
+    ) callconv(.c) c_int {
+        _ = easy;
+        _ = socketp;
+        const ctx = userp orelse return 0;
+        const runtime_ctx: *RuntimeContext = @ptrCast(@alignCast(ctx));
+
+        const what = std.meta.intToEnum(libcurl.CurlPoll, what_raw) catch return 0;
+        if (what == .remove) {
+            runtime_ctx.runtime.remove(@intCast(s));
+            return 0;
+        }
+
+        runtime_ctx.runtime.add(
+            @intCast(s),
+            curlPollToRuntimeEvents(what),
+            runtime_ctx,
+            onRuntimeFdEvent,
+        ) catch {};
+        return 0;
+    }
+
+    fn onCurlTimer(
+        multi: ?*libcurl.CurlM,
+        timeout_ms: c_long,
+        userp: ?*anyopaque,
+    ) callconv(.c) c_int {
+        _ = multi;
+        const ctx = userp orelse return 0;
+        const runtime_ctx: *RuntimeContext = @ptrCast(@alignCast(ctx));
+
+        if (timeout_ms < 0) {
+            runtime_ctx.timer_deadline_ms = null;
+            return 0;
+        }
+
+        runtime_ctx.timer_deadline_ms = std.time.milliTimestamp() + @as(i64, @intCast(timeout_ms));
+        return 0;
+    }
 };
 
 // TODO: on BSD / Linux, we could just read the PEM file directly.
@@ -1381,6 +1547,168 @@ pub const WsConnection = struct {
     }
 };
 
+pub const RuntimeEvent = struct {
+    fd: posix.fd_t,
+    events: u32,
+};
+
+pub const Runtime = if (builtin.target.os.tag == .linux) LinuxRuntime else struct {
+    pub const READABLE: u32 = 0;
+    pub const WRITABLE: u32 = 0;
+    pub const ERROR: u32 = 0;
+    pub const EventCallback = *const fn (ctx: *anyopaque, event: RuntimeEvent) anyerror!void;
+    pub fn init(_: Allocator) !@This() {
+        return error.UnsupportedPlatform;
+    }
+    pub fn deinit(_: *@This()) void {}
+    pub fn add(_: *@This(), _: posix.fd_t, _: u32, _: *anyopaque, _: EventCallback) !void {
+        return error.UnsupportedPlatform;
+    }
+    pub fn remove(_: *@This(), _: posix.fd_t) void {}
+    pub fn removeByCtx(_: *@This(), _: *anyopaque) void {}
+    pub fn dispatch(_: *@This(), _: i32) !usize {
+        return error.UnsupportedPlatform;
+    }
+    pub fn dispatchFor(_: *@This(), _: i32, _: ?posix.fd_t) !bool {
+        return error.UnsupportedPlatform;
+    }
+    pub fn run(_: *@This(), _: *anyopaque, _: *const fn (ctx: *anyopaque) bool) !void {
+        return error.UnsupportedPlatform;
+    }
+};
+
+var runtime_active = std.atomic.Value(bool).init(false);
+
+const LinuxRuntime = struct {
+    pub const READABLE: u32 = linux.EPOLL.IN;
+    pub const WRITABLE: u32 = linux.EPOLL.OUT;
+    pub const ERROR: u32 = linux.EPOLL.ERR | linux.EPOLL.HUP | linux.EPOLL.RDHUP;
+
+    allocator: Allocator,
+    epoll_fd: posix.fd_t,
+    watchers: std.AutoHashMapUnmanaged(posix.fd_t, Watcher) = .empty,
+    events: [64]posix.system.epoll_event = undefined,
+
+    const Self = @This();
+
+    pub const EventCallback = *const fn (ctx: *anyopaque, event: RuntimeEvent) anyerror!void;
+
+    const Watcher = struct {
+        events: u32,
+        ctx: *anyopaque,
+        cb: EventCallback,
+    };
+
+    pub fn init(allocator: Allocator) !Self {
+        if (runtime_active.swap(true, .acq_rel)) {
+            return error.RuntimeAlreadyActive;
+        }
+        errdefer _ = runtime_active.swap(false, .acq_rel);
+
+        const epoll_fd = try posix.epoll_create1(linux.EPOLL.CLOEXEC);
+        errdefer posix.close(epoll_fd);
+
+        return .{
+            .allocator = allocator,
+            .epoll_fd = epoll_fd,
+        };
+    }
+
+    pub fn deinit(self: *Self) void {
+        self.watchers.deinit(self.allocator);
+        posix.close(self.epoll_fd);
+        _ = runtime_active.swap(false, .acq_rel);
+    }
+
+    pub fn add(self: *Self, fd: posix.fd_t, events: u32, ctx: *anyopaque, cb: EventCallback) !void {
+        var ev = posix.system.epoll_event{
+            .events = events,
+            .data = .{ .fd = fd },
+        };
+
+        const gop = try self.watchers.getOrPut(self.allocator, fd);
+        if (gop.found_existing) {
+            gop.value_ptr.* = .{ .events = events, .ctx = ctx, .cb = cb };
+            try posix.epoll_ctl(self.epoll_fd, linux.EPOLL.CTL_MOD, fd, &ev);
+            return;
+        }
+
+        errdefer _ = self.watchers.remove(fd);
+        gop.value_ptr.* = .{ .events = events, .ctx = ctx, .cb = cb };
+        try posix.epoll_ctl(self.epoll_fd, linux.EPOLL.CTL_ADD, fd, &ev);
+    }
+
+    pub fn remove(self: *Self, fd: posix.fd_t) void {
+        _ = self.watchers.remove(fd);
+        posix.epoll_ctl(self.epoll_fd, linux.EPOLL.CTL_DEL, fd, null) catch {};
+    }
+
+    pub fn removeByCtx(self: *Self, ctx: *anyopaque) void {
+        while (true) {
+            var found: ?posix.fd_t = null;
+            var it = self.watchers.iterator();
+            while (it.next()) |entry| {
+                if (entry.value_ptr.ctx == ctx) {
+                    found = entry.key_ptr.*;
+                    break;
+                }
+            }
+            const fd = found orelse break;
+            self.remove(fd);
+        }
+    }
+
+    pub fn run(self: *Self, stop_ctx: *anyopaque, should_stop: *const fn (ctx: *anyopaque) bool) !void {
+        while (!should_stop(stop_ctx)) {
+            _ = try self.dispatch(200);
+        }
+    }
+
+    pub fn dispatch(self: *Self, timeout_ms: i32) !usize {
+        const n = posix.epoll_wait(self.epoll_fd, self.events[0..], timeout_ms);
+        var i: usize = 0;
+        while (i < n) : (i += 1) {
+            const ev = self.events[i];
+            const fd = ev.data.fd;
+
+            const watcher = self.watchers.get(fd) orelse continue;
+            watcher.cb(watcher.ctx, .{
+                .fd = fd,
+                .events = ev.events,
+            }) catch |err| {
+                log.err(.app, "runtime callback", .{ .err = err, .fd = fd });
+                self.remove(fd);
+            };
+        }
+        return n;
+    }
+
+    pub fn dispatchFor(self: *Self, timeout_ms: i32, watched_fd: ?posix.fd_t) !bool {
+        const n = posix.epoll_wait(self.epoll_fd, self.events[0..], timeout_ms);
+        var watched_ready = false;
+        var i: usize = 0;
+        while (i < n) : (i += 1) {
+            const ev = self.events[i];
+            const fd = ev.data.fd;
+            if (watched_fd) |wfd| {
+                if (fd == wfd) {
+                    watched_ready = true;
+                }
+            }
+
+            const watcher = self.watchers.get(fd) orelse continue;
+            watcher.cb(watcher.ctx, .{
+                .fd = fd,
+                .events = ev.events,
+            }) catch |err| {
+                log.err(.app, "runtime callback", .{ .err = err, .fd = fd });
+                self.remove(fd);
+            };
+        }
+        return watched_ready;
+    }
+};
+
 const testing = std.testing;
 
 test "mask" {
diff --git a/src/Server.zig b/src/Server.zig
index bd990560..ada4a576 100644
--- a/src/Server.zig
+++ b/src/Server.zig
@@ -121,26 +121,53 @@ pub fn run(self: *Server, address: net.Address, timeout_ms: u32) !void {
     try posix.listen(listener, self.app.config.maxPendingConnections());
 
     log.info(.app, "server running", .{ .address = address });
-    while (!self.shutdown.load(.acquire)) {
-        const socket = posix.accept(listener, null, null, posix.SOCK.NONBLOCK) catch |err| {
-            switch (err) {
-                error.SocketNotListening, error.ConnectionAborted => {
-                    log.info(.app, "server stopped", .{});
-                    break;
-                },
-                error.WouldBlock => {
-                    std.Thread.sleep(10 * std.time.ns_per_ms);
-                    continue;
-                },
-                else => {
-                    log.err(.app, "CDP accept", .{ .err = err });
-                    std.Thread.sleep(std.time.ns_per_s);
-                    continue;
-                },
-            }
+
+    var runtime = try Net.Runtime.init(self.allocator);
+    defer runtime.deinit();
+
+    var accept_ctx: AcceptCtx = .{
+        .server = self,
+        .timeout_ms = timeout_ms,
+    };
+
+    try runtime.add(listener, Net.Runtime.READABLE, &accept_ctx, onListenerEvent);
+    defer runtime.remove(listener);
+
+    runtime.run(self, shouldStopRuntime) catch |err| switch (err) {
+        error.UnsupportedPlatform => return err,
+        else => return err,
+    };
+
+    log.info(.app, "server stopped", .{});
+}
+
+const AcceptCtx = struct {
+    server: *Server,
+    timeout_ms: u32,
+};
+
+fn shouldStopRuntime(ctx: *anyopaque) bool {
+    const self: *Server = @ptrCast(@alignCast(ctx));
+    return self.shutdown.load(.acquire);
+}
+
+fn onListenerEvent(ctx: *anyopaque, event: Net.RuntimeEvent) !void {
+    _ = event;
+    const accept_ctx: *AcceptCtx = @ptrCast(@alignCast(ctx));
+    const self = accept_ctx.server;
+    const listener = self.listener orelse return;
+
+    while (true) {
+        const socket = posix.accept(listener, null, null, posix.SOCK.NONBLOCK) catch |err| switch (err) {
+            error.WouldBlock => return,
+            error.SocketNotListening, error.ConnectionAborted => return,
+            else => {
+                log.err(.app, "CDP accept", .{ .err = err });
+                return;
+            },
         };
 
-        self.spawnWorker(socket, timeout_ms) catch |err| {
+        self.spawnWorker(socket, accept_ctx.timeout_ms) catch |err| {
             log.err(.app, "CDP spawn", .{ .err = err });
             posix.close(socket);
         };
diff --git a/src/http/Client.zig b/src/http/Client.zig
index 326635f4..9b8feec4 100644
--- a/src/http/Client.zig
+++ b/src/http/Client.zig
@@ -173,6 +173,14 @@ pub fn newHeaders(self: *const Client) !Net.Headers {
     return Net.Headers.init(self.config.http_headers.user_agent_header);
 }
 
+pub fn attachRuntime(self: *Client, runtime: *Net.Runtime, cdp_fd: ?posix.fd_t) !void {
+    try self.handles.attachRuntime(runtime, cdp_fd);
+}
+
+pub fn detachRuntime(self: *Client) void {
+    self.handles.detachRuntime();
+}
+
 pub fn abort(self: *Client) void {
     self._abort(true, 0);
 }
diff --git a/src/sys/libcurl.zig b/src/sys/libcurl.zig
index ca718ebb..73716665 100644
--- a/src/sys/libcurl.zig
+++ b/src/sys/libcurl.zig
@@ -39,7 +39,32 @@ pub const CurlOffT = c.curl_off_t;
 pub const CurlDebugFunction = fn (*Curl, CurlInfoType, [*c]u8, usize, *anyopaque) c_int;
 pub const CurlHeaderFunction = fn ([*]const u8, usize, usize, *anyopaque) usize;
 pub const CurlWriteFunction = fn ([*]const u8, usize, usize, *anyopaque) usize;
+pub const CurlSocketCallback = fn (?*Curl, CurlSocket, c_int, ?*anyopaque, ?*anyopaque) callconv(.c) c_int;
+pub const CurlTimerCallback = fn (?*CurlM, c_long, ?*anyopaque) callconv(.c) c_int;
 pub const curl_writefunc_error: usize = c.CURL_WRITEFUNC_ERROR;
+pub const CURL_SOCKET_TIMEOUT: CurlSocket = c.CURL_SOCKET_TIMEOUT;
+
+pub const CurlPoll = enum(c_int) {
+    in = c.CURL_POLL_IN,
+    out = c.CURL_POLL_OUT,
+    inout = c.CURL_POLL_INOUT,
+    remove = c.CURL_POLL_REMOVE,
+};
+
+pub const CurlSelectMask = packed struct(c_int) {
+    in: bool = false,
+    out: bool = false,
+    err: bool = false,
+    _reserved: std.meta.Int(.unsigned, @bitSizeOf(c_int) - 3) = 0,
+
+    pub fn toC(self: @This()) c_int {
+        var mask: c_int = 0;
+        if (self.in) mask |= c.CURL_CSELECT_IN;
+        if (self.out) mask |= c.CURL_CSELECT_OUT;
+        if (self.err) mask |= c.CURL_CSELECT_ERR;
+        return mask;
+    }
+};
 
 pub const CurlGlobalFlags = packed struct(u8) {
     ssl: bool = false,
@@ -156,6 +181,10 @@ pub const CurlOption = enum(c.CURLoption) {
 
 pub const CurlMOption = enum(c.CURLMoption) {
     max_host_connections = c.CURLMOPT_MAX_HOST_CONNECTIONS,
+    socket_function = c.CURLMOPT_SOCKETFUNCTION,
+    socket_data = c.CURLMOPT_SOCKETDATA,
+    timer_function = c.CURLMOPT_TIMERFUNCTION,
+    timer_data = c.CURLMOPT_TIMERDATA,
 };
 
 pub const CurlInfo = enum(c.CURLINFO) {
@@ -675,6 +704,10 @@ pub fn curl_multi_setopt(multi: *CurlM, comptime option: CurlMOption, value: any
             };
             break :blk c.curl_multi_setopt(multi, opt, n);
         },
+        .socket_function => c.curl_multi_setopt(multi, opt, value),
+        .socket_data => c.curl_multi_setopt(multi, opt, value),
+        .timer_function => c.curl_multi_setopt(multi, opt, value),
+        .timer_data => c.curl_multi_setopt(multi, opt, value),
     };
     try errorMCheck(code);
 }
@@ -701,6 +734,15 @@ pub fn curl_multi_poll(
     try errorMCheck(c.curl_multi_poll(multi, raw_fds, @intCast(extra_fds.len), timeout_ms, numfds));
 }
 
+pub fn curl_multi_socket_action(
+    multi: *CurlM,
+    s: CurlSocket,
+    ev_bitmask: c_int,
+    running_handles: *c_int,
+) ErrorMulti!void {
+    try errorMCheck(c.curl_multi_socket_action(multi, s, ev_bitmask, running_handles));
+}
+
 pub fn curl_multi_info_read(multi: *CurlM, msgs_in_queue: *c_int) ?CurlMsg {
     const ptr = c.curl_multi_info_read(multi, msgs_in_queue);
     if (ptr == null) return null;