Merge branch 'lun-4-net-reuseaddr-opt'

Closes #3820

Author: andrewrk

lib/std/c.zig

@@ -120,7 +120,8 @@ pub extern "c" fn listen(sockfd: fd_t, backlog: c_uint) c_int;
 pub extern "c" fn getsockname(sockfd: fd_t, noalias addr: *sockaddr, noalias addrlen: *socklen_t) c_int;
 pub extern "c" fn connect(sockfd: fd_t, sock_addr: *const sockaddr, addrlen: socklen_t) c_int;
 pub extern "c" fn accept4(sockfd: fd_t, addr: *sockaddr, addrlen: *socklen_t, flags: c_uint) c_int;
-pub extern "c" fn getsockopt(sockfd: fd_t, level: c_int, optname: c_int, optval: *c_void, optlen: *socklen_t) c_int;
+pub extern "c" fn getsockopt(sockfd: fd_t, level: u32, optname: u32, optval: *c_void, optlen: *socklen_t) c_int;
+pub extern "c" fn setsockopt(sockfd: fd_t, level: u32, optname: u32, optval: *c_void, optlen: socklen_t) c_int;
 pub extern "c" fn send(sockfd: fd_t, buf: *const c_void, len: usize, flags: u32) isize;
 pub extern "c" fn sendto(
     sockfd: fd_t,

lib/std/net.zig

@@ -1279,6 +1279,7 @@ fn dnsParseCallback(ctx: dpc_ctx, rr: u8, data: []const u8, packet: []const u8)
 pub const StreamServer = struct {
     /// Copied from `Options` on `init`.
     kernel_backlog: u32,
+    reuse_address: bool,
 
     /// `undefined` until `listen` returns successfully.
     listen_address: Address,
@@ -1290,6 +1291,9 @@ pub const StreamServer = struct {
         /// If more than this many connections pool in the kernel, clients will start
         /// seeing "Connection refused".
         kernel_backlog: u32 = 128,
+
+        /// Enable SO_REUSEADDR on the socket.
+        reuse_address: bool = false,
     };
 
     /// After this call succeeds, resources have been acquired and must
@@ -1298,6 +1302,7 @@ pub const StreamServer = struct {
         return StreamServer{
             .sockfd = null,
             .kernel_backlog = options.kernel_backlog,
+            .reuse_address = options.reuse_address,
             .listen_address = undefined,
         };
     }
@@ -1320,6 +1325,15 @@ pub const StreamServer = struct {
             self.sockfd = null;
         }
 
+        if (self.reuse_address) {
+            try os.setsockopt(
+                self.sockfd.?,
+                os.SOL_SOCKET,
+                os.SO_REUSEADDR,
+                &mem.toBytes(@as(c_int, 1)),
+            );
+        }
+
         var socklen = address.getOsSockLen();
         try os.bind(sockfd, &address.any, socklen);
         try os.listen(sockfd, self.kernel_backlog);

lib/std/os.zig

@@ -3250,3 +3250,34 @@ pub fn sched_yield() SchedYieldError!void {
         else => return error.SystemCannotYield,
     }
 }
+
+pub const SetSockOptError = error{
+    /// The socket is already connected, and a specified option cannot be set while the socket is connected.
+    AlreadyConnected,
+
+    /// The option is not supported by the protocol.
+    InvalidProtocolOption,
+
+    /// The send and receive timeout values are too big to fit into the timeout fields in the socket structure.
+    TimeoutTooBig,
+
+    /// Insufficient resources are available in the system to complete the call.
+    SystemResources,
+} || UnexpectedError;
+
+/// Set a socket's options.
+pub fn setsockopt(fd: fd_t, level: u32, optname: u32, opt: []const u8) SetSockOptError!void {
+    switch (errno(system.setsockopt(fd, level, optname, opt.ptr, @intCast(socklen_t, opt.len)))) {
+        0 => {},
+        EBADF => unreachable, // always a race condition
+        ENOTSOCK => unreachable, // always a race condition
+        EINVAL => unreachable,
+        EFAULT => unreachable,
+        EDOM => return error.TimeoutTooBig,
+        EISCONN => return error.AlreadyConnected,
+        ENOPROTOOPT => return error.InvalidProtocolOption,
+        ENOMEM => return error.SystemResources,
+        ENOBUFS => return error.SystemResources,
+        else => |err| return unexpectedErrno(err),
+    }
+}