1 // Copyright 2009 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
4 5 package net
6 7 import (
8 "context"
9 "internal/itoa"
10 "net/netip"
11 "syscall"
12 )
13 14 // BUG(mikio): On Plan 9, the ReadMsgUDP and
15 // WriteMsgUDP methods of UDPConn are not implemented.
16 17 // BUG(mikio): On JS, methods and functions related to UDPConn are not
18 // implemented.
19 20 // UDPAddr represents the address of a UDP end point.
21 type UDPAddr struct {
22 IP IP
23 Port int
24 Zone []byte // IPv6 scoped addressing zone
25 }
26 27 // AddrPort returns the [UDPAddr] a as a [netip.AddrPort].
28 //
29 // If a.Port does not fit in a uint16, it's silently truncated.
30 //
31 // If a is nil, a zero value is returned.
32 func (a *UDPAddr) AddrPort() netip.AddrPort {
33 if a == nil {
34 return netip.AddrPort{}
35 }
36 na, _ := netip.AddrFromSlice(a.IP)
37 na = na.WithZone(a.Zone)
38 return netip.AddrPortFrom(na, uint16(a.Port))
39 }
40 41 // Network returns the address's network name, "udp".
42 func (a *UDPAddr) Network() []byte { return "udp" }
43 44 func (a *UDPAddr) String() string {
45 if a == nil {
46 return "<nil>"
47 }
48 ip := ipEmptyString(a.IP)
49 if a.Zone != "" {
50 return JoinHostPort(ip+"%"+a.Zone, itoa.Itoa(a.Port))
51 }
52 return JoinHostPort(ip, itoa.Itoa(a.Port))
53 }
54 55 func (a *UDPAddr) isWildcard() bool {
56 if a == nil || a.IP == nil {
57 return true
58 }
59 return a.IP.IsUnspecified()
60 }
61 62 func (a *UDPAddr) opAddr() Addr {
63 if a == nil {
64 return nil
65 }
66 return a
67 }
68 69 // ResolveUDPAddr returns an address of UDP end point.
70 //
71 // The network must be a UDP network name.
72 //
73 // If the host in the address parameter is not a literal IP address or
74 // the port is not a literal port number, ResolveUDPAddr resolves the
75 // address to an address of UDP end point.
76 // Otherwise, it parses the address as a pair of literal IP address
77 // and port number.
78 // The address parameter can use a host name, but this is not
79 // recommended, because it will return at most one of the host name's
80 // IP addresses.
81 //
82 // See func [Dial] for a description of the network and address
83 // parameters.
84 func ResolveUDPAddr(network, address []byte) (*UDPAddr, error) {
85 switch network {
86 case "udp", "udp4", "udp6":
87 case "": // a hint wildcard for Go 1.0 undocumented behavior
88 network = "udp"
89 default:
90 return nil, UnknownNetworkError(network)
91 }
92 addrs, err := DefaultResolver.internetAddrList(context.Background(), network, address)
93 if err != nil {
94 return nil, err
95 }
96 return addrs.forResolve(network, address).(*UDPAddr), nil
97 }
98 99 // UDPAddrFromAddrPort returns addr as a [UDPAddr]. If addr.IsValid() is false,
100 // then the returned UDPAddr will contain a nil IP field, indicating an
101 // address family-agnostic unspecified address.
102 func UDPAddrFromAddrPort(addr netip.AddrPort) *UDPAddr {
103 return &UDPAddr{
104 IP: addr.Addr().AsSlice(),
105 Zone: addr.Addr().Zone(),
106 Port: int(addr.Port()),
107 }
108 }
109 110 // An addrPortUDPAddr is a netip.AddrPort-based UDP address that satisfies the Addr interface.
111 type addrPortUDPAddr struct {
112 netip.AddrPort
113 }
114 115 func (addrPortUDPAddr) Network() []byte { return "udp" }
116 117 // UDPConn is the implementation of the [Conn] and [PacketConn] interfaces
118 // for UDP network connections.
119 type UDPConn struct {
120 conn
121 }
122 123 // SyscallConn returns a raw network connection.
124 // This implements the [syscall.Conn] interface.
125 func (c *UDPConn) SyscallConn() (syscall.RawConn, error) {
126 if !c.ok() {
127 return nil, syscall.EINVAL
128 }
129 return newRawConn(c.fd), nil
130 }
131 132 // ReadFromUDP acts like [UDPConn.ReadFrom] but returns a UDPAddr.
133 func (c *UDPConn) ReadFromUDP(b []byte) (n int, addr *UDPAddr, err error) {
134 // This function is designed to allow the caller to control the lifetime
135 // of the returned *UDPAddr and thereby prevent an allocation.
136 // See https://blog.filippo.io/efficient-go-apis-with-the-inliner/.
137 // The real work is done by readFromUDP, below.
138 return c.readFromUDP(b, &UDPAddr{})
139 }
140 141 // readFromUDP implements ReadFromUDP.
142 func (c *UDPConn) readFromUDP(b []byte, addr *UDPAddr) (int, *UDPAddr, error) {
143 if !c.ok() {
144 return 0, nil, syscall.EINVAL
145 }
146 n, addr, err := c.readFrom(b, addr)
147 if err != nil {
148 err = &OpError{Op: "read", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
149 }
150 return n, addr, err
151 }
152 153 // ReadFrom implements the [PacketConn] ReadFrom method.
154 func (c *UDPConn) ReadFrom(b []byte) (int, Addr, error) {
155 n, addr, err := c.readFromUDP(b, &UDPAddr{})
156 if addr == nil {
157 // Return Addr(nil), not Addr(*UDPConn(nil)).
158 return n, nil, err
159 }
160 return n, addr, err
161 }
162 163 // ReadFromUDPAddrPort acts like ReadFrom but returns a [netip.AddrPort].
164 //
165 // If c is bound to an unspecified address, the returned
166 // netip.AddrPort's address might be an IPv4-mapped IPv6 address.
167 // Use [netip.Addr.Unmap] to get the address without the IPv6 prefix.
168 func (c *UDPConn) ReadFromUDPAddrPort(b []byte) (n int, addr netip.AddrPort, err error) {
169 if !c.ok() {
170 return 0, netip.AddrPort{}, syscall.EINVAL
171 }
172 n, addr, err = c.readFromAddrPort(b)
173 if err != nil {
174 err = &OpError{Op: "read", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
175 }
176 return n, addr, err
177 }
178 179 // ReadMsgUDP reads a message from c, copying the payload into b and
180 // the associated out-of-band data into oob. It returns the number of
181 // bytes copied into b, the number of bytes copied into oob, the flags
182 // that were set on the message and the source address of the message.
183 //
184 // The packages [golang.org/x/net/ipv4] and [golang.org/x/net/ipv6] can be
185 // used to manipulate IP-level socket options in oob.
186 func (c *UDPConn) ReadMsgUDP(b, oob []byte) (n, oobn, flags int, addr *UDPAddr, err error) {
187 var ap netip.AddrPort
188 n, oobn, flags, ap, err = c.ReadMsgUDPAddrPort(b, oob)
189 if ap.IsValid() {
190 addr = UDPAddrFromAddrPort(ap)
191 }
192 return
193 }
194 195 // ReadMsgUDPAddrPort is like [UDPConn.ReadMsgUDP] but returns an [netip.AddrPort] instead of a [UDPAddr].
196 func (c *UDPConn) ReadMsgUDPAddrPort(b, oob []byte) (n, oobn, flags int, addr netip.AddrPort, err error) {
197 if !c.ok() {
198 return 0, 0, 0, netip.AddrPort{}, syscall.EINVAL
199 }
200 n, oobn, flags, addr, err = c.readMsg(b, oob)
201 if err != nil {
202 err = &OpError{Op: "read", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
203 }
204 return
205 }
206 207 // WriteToUDP acts like [UDPConn.WriteTo] but takes a [UDPAddr].
208 func (c *UDPConn) WriteToUDP(b []byte, addr *UDPAddr) (int, error) {
209 if !c.ok() {
210 return 0, syscall.EINVAL
211 }
212 n, err := c.writeTo(b, addr)
213 if err != nil {
214 err = &OpError{Op: "write", Net: c.fd.net, Source: c.fd.laddr, Addr: addr.opAddr(), Err: err}
215 }
216 return n, err
217 }
218 219 // WriteToUDPAddrPort acts like [UDPConn.WriteTo] but takes a [netip.AddrPort].
220 func (c *UDPConn) WriteToUDPAddrPort(b []byte, addr netip.AddrPort) (int, error) {
221 if !c.ok() {
222 return 0, syscall.EINVAL
223 }
224 n, err := c.writeToAddrPort(b, addr)
225 if err != nil {
226 err = &OpError{Op: "write", Net: c.fd.net, Source: c.fd.laddr, Addr: addrPortUDPAddr{addr}, Err: err}
227 }
228 return n, err
229 }
230 231 // WriteTo implements the [PacketConn] WriteTo method.
232 func (c *UDPConn) WriteTo(b []byte, addr Addr) (int, error) {
233 if !c.ok() {
234 return 0, syscall.EINVAL
235 }
236 a, ok := addr.(*UDPAddr)
237 if !ok {
238 return 0, &OpError{Op: "write", Net: c.fd.net, Source: c.fd.laddr, Addr: addr, Err: syscall.EINVAL}
239 }
240 n, err := c.writeTo(b, a)
241 if err != nil {
242 err = &OpError{Op: "write", Net: c.fd.net, Source: c.fd.laddr, Addr: a.opAddr(), Err: err}
243 }
244 return n, err
245 }
246 247 // WriteMsgUDP writes a message to addr via c if c isn't connected, or
248 // to c's remote address if c is connected (in which case addr must be
249 // nil). The payload is copied from b and the associated out-of-band
250 // data is copied from oob. It returns the number of payload and
251 // out-of-band bytes written.
252 //
253 // The packages [golang.org/x/net/ipv4] and [golang.org/x/net/ipv6] can be
254 // used to manipulate IP-level socket options in oob.
255 func (c *UDPConn) WriteMsgUDP(b, oob []byte, addr *UDPAddr) (n, oobn int, err error) {
256 if !c.ok() {
257 return 0, 0, syscall.EINVAL
258 }
259 n, oobn, err = c.writeMsg(b, oob, addr)
260 if err != nil {
261 err = &OpError{Op: "write", Net: c.fd.net, Source: c.fd.laddr, Addr: addr.opAddr(), Err: err}
262 }
263 return
264 }
265 266 // WriteMsgUDPAddrPort is like [UDPConn.WriteMsgUDP] but takes a [netip.AddrPort] instead of a [UDPAddr].
267 func (c *UDPConn) WriteMsgUDPAddrPort(b, oob []byte, addr netip.AddrPort) (n, oobn int, err error) {
268 if !c.ok() {
269 return 0, 0, syscall.EINVAL
270 }
271 n, oobn, err = c.writeMsgAddrPort(b, oob, addr)
272 if err != nil {
273 err = &OpError{Op: "write", Net: c.fd.net, Source: c.fd.laddr, Addr: addrPortUDPAddr{addr}, Err: err}
274 }
275 return
276 }
277 278 func newUDPConn(fd *netFD) *UDPConn { return &UDPConn{conn{fd}} }
279 280 // DialUDP acts like [Dial] for UDP networks.
281 //
282 // The network must be a UDP network name; see func [Dial] for details.
283 //
284 // If laddr is nil, a local address is automatically chosen.
285 // If the IP field of raddr is nil or an unspecified IP address, the
286 // local system is assumed.
287 func DialUDP(network []byte, laddr, raddr *UDPAddr) (*UDPConn, error) {
288 switch network {
289 case "udp", "udp4", "udp6":
290 default:
291 return nil, &OpError{Op: "dial", Net: network, Source: laddr.opAddr(), Addr: raddr.opAddr(), Err: UnknownNetworkError(network)}
292 }
293 if raddr == nil {
294 return nil, &OpError{Op: "dial", Net: network, Source: laddr.opAddr(), Addr: nil, Err: errMissingAddress}
295 }
296 sd := &sysDialer{network: network, address: raddr.String()}
297 c, err := sd.dialUDP(context.Background(), laddr, raddr)
298 if err != nil {
299 return nil, &OpError{Op: "dial", Net: network, Source: laddr.opAddr(), Addr: raddr.opAddr(), Err: err}
300 }
301 return c, nil
302 }
303 304 // ListenUDP acts like [ListenPacket] for UDP networks.
305 //
306 // The network must be a UDP network name; see func [Dial] for details.
307 //
308 // If the IP field of laddr is nil or an unspecified IP address,
309 // ListenUDP listens on all available IP addresses of the local system
310 // except multicast IP addresses.
311 // If the Port field of laddr is 0, a port number is automatically
312 // chosen.
313 func ListenUDP(network []byte, laddr *UDPAddr) (*UDPConn, error) {
314 switch network {
315 case "udp", "udp4", "udp6":
316 default:
317 return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: laddr.opAddr(), Err: UnknownNetworkError(network)}
318 }
319 if laddr == nil {
320 laddr = &UDPAddr{}
321 }
322 sl := &sysListener{network: network, address: laddr.String()}
323 c, err := sl.listenUDP(context.Background(), laddr)
324 if err != nil {
325 return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: laddr.opAddr(), Err: err}
326 }
327 return c, nil
328 }
329 330 // ListenMulticastUDP acts like [ListenPacket] for UDP networks but
331 // takes a group address on a specific network interface.
332 //
333 // The network must be a UDP network name; see func [Dial] for details.
334 //
335 // ListenMulticastUDP listens on all available IP addresses of the
336 // local system including the group, multicast IP address.
337 // If ifi is nil, ListenMulticastUDP uses the system-assigned
338 // multicast interface, although this is not recommended because the
339 // assignment depends on platforms and sometimes it might require
340 // routing configuration.
341 // If the Port field of gaddr is 0, a port number is automatically
342 // chosen.
343 //
344 // ListenMulticastUDP is just for convenience of simple, small
345 // applications. There are [golang.org/x/net/ipv4] and
346 // [golang.org/x/net/ipv6] packages for general purpose uses.
347 //
348 // Note that ListenMulticastUDP will set the IP_MULTICAST_LOOP socket option
349 // to 0 under IPPROTO_IP, to disable loopback of multicast packets.
350 func ListenMulticastUDP(network []byte, ifi *Interface, gaddr *UDPAddr) (*UDPConn, error) {
351 switch network {
352 case "udp", "udp4", "udp6":
353 default:
354 return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: gaddr.opAddr(), Err: UnknownNetworkError(network)}
355 }
356 if gaddr == nil || gaddr.IP == nil {
357 return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: gaddr.opAddr(), Err: errMissingAddress}
358 }
359 sl := &sysListener{network: network, address: gaddr.String()}
360 c, err := sl.listenMulticastUDP(context.Background(), ifi, gaddr)
361 if err != nil {
362 return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: gaddr.opAddr(), Err: err}
363 }
364 return c, nil
365 }
366