OXIESEC PANEL

Name	Size	Modified	Perms
📁 ..	-	12/01/2022 06:13:58 PM	rwxr-xr-x
📄 addrselect.go	9.44 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 addrselect_test.go	6.22 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 cgo_aix.go	582 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 cgo_android.go	272 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 cgo_bsd.go	353 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 cgo_linux.go	642 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 cgo_netbsd.go	276 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 cgo_openbsd.go	276 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 cgo_resnew.go	590 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 cgo_resold.go	579 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 cgo_socknew.go	753 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 cgo_sockold.go	852 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 cgo_solaris.go	343 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 cgo_stub.go	1.03 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 cgo_unix.go	9.49 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 cgo_unix_test.go	1.84 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 cgo_windows.go	402 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 conf.go	9.65 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 conf_netcgo.go	370 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 conf_test.go	9.7 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 conn_test.go	1.73 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 dial.go	22.73 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 dial_test.go	26.1 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 dial_unix_test.go	2.77 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 dnsclient.go	5.57 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 dnsclient_test.go	1.51 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 dnsclient_unix.go	22.72 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 dnsclient_unix_test.go	57.08 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 dnsconfig.go	1.61 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 dnsconfig_unix.go	4.01 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 dnsconfig_unix_test.go	6.69 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 dnsconfig_windows.go	1.42 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 dnsname_test.go	1.98 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 error_plan9.go	224 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 error_plan9_test.go	476 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 error_posix.go	542 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 error_posix_test.go	981 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 error_test.go	19.72 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 error_unix.go	372 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 error_unix_test.go	762 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 error_windows.go	355 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 error_windows_test.go	796 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 example_test.go	8.45 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 external_test.go	4.07 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 fcntl_libc_test.go	374 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 fcntl_syscall_test.go	496 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 fd_plan9.go	3.56 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 fd_posix.go	4.29 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 fd_unix.go	5.37 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 fd_windows.go	4.62 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 file.go	1.69 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 file_plan9.go	2.68 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 file_stub.go	489 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 file_test.go	6.38 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 file_unix.go	2.46 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 file_windows.go	521 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 hook.go	628 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 hook_plan9.go	283 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 hook_unix.go	690 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 hook_windows.go	875 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 hosts.go	3.02 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 hosts_test.go	4.58 KB	12/01/2022 06:12:59 PM	rw-r--r--
📁 http	-	12/01/2022 06:13:56 PM	rwxr-xr-x
📄 interface.go	7.17 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 interface_aix.go	4.4 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 interface_bsd.go	2.76 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 interface_bsd_test.go	1.44 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 interface_bsdvar.go	718 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 interface_darwin.go	1.29 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 interface_freebsd.go	1.29 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 interface_linux.go	6.9 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 interface_linux_test.go	3.65 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 interface_plan9.go	4.68 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 interface_solaris.go	2.07 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 interface_stub.go	812 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 interface_test.go	9.67 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 interface_unix_test.go	4.73 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 interface_windows.go	5.41 KB	12/01/2022 06:12:59 PM	rw-r--r--
📁 internal	-	12/01/2022 06:13:56 PM	rwxr-xr-x
📄 ip.go	17.72 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 ip_test.go	25.33 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 iprawsock.go	7.08 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 iprawsock_plan9.go	874 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 iprawsock_posix.go	3.41 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 iprawsock_test.go	5.62 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 ipsock.go	8.97 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 ipsock_plan9.go	7.5 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 ipsock_plan9_test.go	645 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 ipsock_posix.go	7.66 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 ipsock_test.go	6.81 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 listen_test.go	20.51 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 lookup.go	27.82 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 lookup_fake.go	1.64 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 lookup_plan9.go	8.86 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 lookup_test.go	35.13 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 lookup_unix.go	4.46 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 lookup_windows.go	12.53 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 lookup_windows_test.go	8.5 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 mac.go	1.88 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 mac_test.go	3.26 KB	12/01/2022 06:12:59 PM	rw-r--r--
📁 mail	-	12/01/2022 06:13:56 PM	rwxr-xr-x
📄 main_cloexec_test.go	693 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 main_conf_test.go	922 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 main_noconf_test.go	505 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 main_plan9_test.go	392 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 main_posix_test.go	1.38 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 main_test.go	7.08 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 main_unix_test.go	1.19 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 main_windows_test.go	1.08 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 mockserver_test.go	10.79 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 net.go	23.25 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 net_fake.go	6.59 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 net_test.go	13.88 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 net_windows_test.go	16.28 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 netgo.go	427 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 netgo_unix_test.go	656 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📁 netip	-	12/01/2022 06:13:56 PM	rwxr-xr-x
📄 nss.go	3.64 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 nss_test.go	3.35 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 packetconn_test.go	3.03 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 parse.go	7.06 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 parse_test.go	1.46 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 pipe.go	5.43 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 pipe_test.go	1.2 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 platform_test.go	4.57 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 port.go	1.46 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 port_test.go	1.34 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 port_unix.go	1.24 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 protoconn_test.go	7.19 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 rawconn.go	1.89 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 rawconn_stub_test.go	631 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 rawconn_test.go	4.32 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 rawconn_unix_test.go	2.96 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 rawconn_windows_test.go	3.12 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 resolverdialfunc_test.go	8.29 KB	12/01/2022 06:12:59 PM	rw-r--r--
📁 rpc	-	12/01/2022 06:13:56 PM	rwxr-xr-x
📄 sendfile_linux.go	1.1 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 sendfile_stub.go	344 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 sendfile_test.go	6.72 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 sendfile_unix_alt.go	2.01 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 sendfile_windows.go	1.02 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 server_test.go	11.01 KB	12/01/2022 06:12:59 PM	rw-r--r--
📁 smtp	-	12/01/2022 06:13:56 PM	rwxr-xr-x
📄 sock_bsd.go	918 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 sock_cloexec.go	741 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 sock_linux.go	1.53 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 sock_linux_test.go	545 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 sock_plan9.go	262 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 sock_posix.go	6.78 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 sock_stub.go	390 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 sock_windows.go	1.16 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 sockaddr_posix.go	914 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 sockopt_aix.go	1.43 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 sockopt_bsd.go	2.21 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 sockopt_linux.go	1.25 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 sockopt_plan9.go	406 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 sockopt_posix.go	2.62 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 sockopt_solaris.go	1.25 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 sockopt_stub.go	742 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 sockopt_windows.go	1.51 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 sockoptip_bsdvar.go	867 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 sockoptip_linux.go	735 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 sockoptip_posix.go	1.38 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 sockoptip_stub.go	767 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 sockoptip_windows.go	819 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 splice_linux.go	1.09 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 splice_stub.go	287 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 splice_test.go	10.05 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 sys_cloexec.go	962 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 tcpsock.go	10.61 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 tcpsock_plan9.go	2.21 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 tcpsock_posix.go	5.31 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 tcpsock_test.go	17.32 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 tcpsock_unix_test.go	2.35 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 tcpsockopt_darwin.go	770 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 tcpsockopt_dragonfly.go	698 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 tcpsockopt_openbsd.go	365 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 tcpsockopt_plan9.go	525 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 tcpsockopt_posix.go	442 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 tcpsockopt_solaris.go	1.15 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 tcpsockopt_stub.go	397 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 tcpsockopt_unix.go	722 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 tcpsockopt_windows.go	741 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📁 testdata	-	12/01/2022 06:13:56 PM	rwxr-xr-x
📁 textproto	-	12/01/2022 06:13:56 PM	rwxr-xr-x
📄 timeout_test.go	28.56 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 udpsock.go	11.83 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 udpsock_plan9.go	4.64 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 udpsock_plan9_test.go	1.31 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 udpsock_posix.go	6.78 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 udpsock_test.go	16.29 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 unixsock.go	10.17 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 unixsock_linux_test.go	2.29 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 unixsock_plan9.go	1.24 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 unixsock_posix.go	5.87 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 unixsock_readmsg_cloexec.go	654 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 unixsock_readmsg_cmsg_cloexec.go	332 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 unixsock_readmsg_other.go	275 bytes	12/01/2022 06:12:59 PM	rw-r--r--
📄 unixsock_readmsg_test.go	2.48 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 unixsock_test.go	10.42 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 unixsock_windows_test.go	2.03 KB	12/01/2022 06:12:59 PM	rw-r--r--
📁 url	-	12/01/2022 06:13:56 PM	rwxr-xr-x
📄 write_unix_test.go	1.61 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 writev_test.go	4.97 KB	12/01/2022 06:12:59 PM	rw-r--r--
📄 writev_unix.go	733 bytes	12/01/2022 06:12:59 PM	rw-r--r--

Editing: ipsock_posix.go

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

//go:build unix || (js && wasm) || windows

package net

import (
	"context"
	"internal/poll"
	"net/netip"
	"runtime"
	"syscall"
)

// probe probes IPv4, IPv6 and IPv4-mapped IPv6 communication
// capabilities which are controlled by the IPV6_V6ONLY socket option
// and kernel configuration.
//
// Should we try to use the IPv4 socket interface if we're only
// dealing with IPv4 sockets? As long as the host system understands
// IPv4-mapped IPv6, it's okay to pass IPv4-mapped IPv6 addresses to
// the IPv6 interface. That simplifies our code and is most
// general. Unfortunately, we need to run on kernels built without
// IPv6 support too. So probe the kernel to figure it out.
func (p *ipStackCapabilities) probe() {
	s, err := sysSocket(syscall.AF_INET, syscall.SOCK_STREAM, syscall.IPPROTO_TCP)
	switch err {
	case syscall.EAFNOSUPPORT, syscall.EPROTONOSUPPORT:
	case nil:
		poll.CloseFunc(s)
		p.ipv4Enabled = true
	}
	var probes = []struct {
		laddr TCPAddr
		value int
	}{
		// IPv6 communication capability
		{laddr: TCPAddr{IP: ParseIP("::1")}, value: 1},
		// IPv4-mapped IPv6 address communication capability
		{laddr: TCPAddr{IP: IPv4(127, 0, 0, 1)}, value: 0},
	}
	switch runtime.GOOS {
	case "dragonfly", "openbsd":
		// The latest DragonFly BSD and OpenBSD kernels don't
		// support IPV6_V6ONLY=0. They always return an error
		// and we don't need to probe the capability.
		probes = probes[:1]
	}
	for i := range probes {
		s, err := sysSocket(syscall.AF_INET6, syscall.SOCK_STREAM, syscall.IPPROTO_TCP)
		if err != nil {
			continue
		}
		defer poll.CloseFunc(s)
		syscall.SetsockoptInt(s, syscall.IPPROTO_IPV6, syscall.IPV6_V6ONLY, probes[i].value)
		sa, err := probes[i].laddr.sockaddr(syscall.AF_INET6)
		if err != nil {
			continue
		}
		if err := syscall.Bind(s, sa); err != nil {
			continue
		}
		if i == 0 {
			p.ipv6Enabled = true
		} else {
			p.ipv4MappedIPv6Enabled = true
		}
	}
}

// favoriteAddrFamily returns the appropriate address family for the
// given network, laddr, raddr and mode.
//
// If mode indicates "listen" and laddr is a wildcard, we assume that
// the user wants to make a passive-open connection with a wildcard
// address family, both AF_INET and AF_INET6, and a wildcard address
// like the following:
//
//   - A listen for a wildcard communication domain, "tcp" or
//     "udp", with a wildcard address: If the platform supports
//     both IPv6 and IPv4-mapped IPv6 communication capabilities,
//     or does not support IPv4, we use a dual stack, AF_INET6 and
//     IPV6_V6ONLY=0, wildcard address listen. The dual stack
//     wildcard address listen may fall back to an IPv6-only,
//     AF_INET6 and IPV6_V6ONLY=1, wildcard address listen.
//     Otherwise we prefer an IPv4-only, AF_INET, wildcard address
//     listen.
//
//   - A listen for a wildcard communication domain, "tcp" or
//     "udp", with an IPv4 wildcard address: same as above.
//
//   - A listen for a wildcard communication domain, "tcp" or
//     "udp", with an IPv6 wildcard address: same as above.
//
//   - A listen for an IPv4 communication domain, "tcp4" or "udp4",
//     with an IPv4 wildcard address: We use an IPv4-only, AF_INET,
//     wildcard address listen.
//
//   - A listen for an IPv6 communication domain, "tcp6" or "udp6",
//     with an IPv6 wildcard address: We use an IPv6-only, AF_INET6
//     and IPV6_V6ONLY=1, wildcard address listen.
//
// Otherwise guess: If the addresses are IPv4 then returns AF_INET,
// or else returns AF_INET6. It also returns a boolean value what
// designates IPV6_V6ONLY option.
//
// Note that the latest DragonFly BSD and OpenBSD kernels allow
// neither "net.inet6.ip6.v6only=1" change nor IPPROTO_IPV6 level
// IPV6_V6ONLY socket option setting.
func favoriteAddrFamily(network string, laddr, raddr sockaddr, mode string) (family int, ipv6only bool) {
	switch network[len(network)-1] {
	case '4':
		return syscall.AF_INET, false
	case '6':
		return syscall.AF_INET6, true
	}

if mode == "listen" && (laddr == nil || laddr.isWildcard()) {
		if supportsIPv4map() || !supportsIPv4() {
			return syscall.AF_INET6, false
		}
		if laddr == nil {
			return syscall.AF_INET, false
		}
		return laddr.family(), false
	}

if (laddr == nil || laddr.family() == syscall.AF_INET) &&
		(raddr == nil || raddr.family() == syscall.AF_INET) {
		return syscall.AF_INET, false
	}
	return syscall.AF_INET6, false
}

func internetSocket(ctx context.Context, net string, laddr, raddr sockaddr, sotype, proto int, mode string, ctrlFn func(string, string, syscall.RawConn) error) (fd *netFD, err error) {
	if (runtime.GOOS == "aix" || runtime.GOOS == "windows" || runtime.GOOS == "openbsd") && mode == "dial" && raddr.isWildcard() {
		raddr = raddr.toLocal(net)
	}
	family, ipv6only := favoriteAddrFamily(net, laddr, raddr, mode)
	return socket(ctx, net, family, sotype, proto, ipv6only, laddr, raddr, ctrlFn)
}

func ipToSockaddrInet4(ip IP, port int) (syscall.SockaddrInet4, error) {
	if len(ip) == 0 {
		ip = IPv4zero
	}
	ip4 := ip.To4()
	if ip4 == nil {
		return syscall.SockaddrInet4{}, &AddrError{Err: "non-IPv4 address", Addr: ip.String()}
	}
	sa := syscall.SockaddrInet4{Port: port}
	copy(sa.Addr[:], ip4)
	return sa, nil
}

func ipToSockaddrInet6(ip IP, port int, zone string) (syscall.SockaddrInet6, error) {
	// In general, an IP wildcard address, which is either
	// "0.0.0.0" or "::", means the entire IP addressing
	// space. For some historical reason, it is used to
	// specify "any available address" on some operations
	// of IP node.
	//
	// When the IP node supports IPv4-mapped IPv6 address,
	// we allow a listener to listen to the wildcard
	// address of both IP addressing spaces by specifying
	// IPv6 wildcard address.
	if len(ip) == 0 || ip.Equal(IPv4zero) {
		ip = IPv6zero
	}
	// We accept any IPv6 address including IPv4-mapped
	// IPv6 address.
	ip6 := ip.To16()
	if ip6 == nil {
		return syscall.SockaddrInet6{}, &AddrError{Err: "non-IPv6 address", Addr: ip.String()}
	}
	sa := syscall.SockaddrInet6{Port: port, ZoneId: uint32(zoneCache.index(zone))}
	copy(sa.Addr[:], ip6)
	return sa, nil
}

func ipToSockaddr(family int, ip IP, port int, zone string) (syscall.Sockaddr, error) {
	switch family {
	case syscall.AF_INET:
		sa, err := ipToSockaddrInet4(ip, port)
		if err != nil {
			return nil, err
		}
		return &sa, nil
	case syscall.AF_INET6:
		sa, err := ipToSockaddrInet6(ip, port, zone)
		if err != nil {
			return nil, err
		}
		return &sa, nil
	}
	return nil, &AddrError{Err: "invalid address family", Addr: ip.String()}
}

func addrPortToSockaddrInet4(ap netip.AddrPort) (syscall.SockaddrInet4, error) {
	// ipToSockaddrInet4 has special handling here for zero length slices.
	// We do not, because netip has no concept of a generic zero IP address.
	addr := ap.Addr()
	if !addr.Is4() {
		return syscall.SockaddrInet4{}, &AddrError{Err: "non-IPv4 address", Addr: addr.String()}
	}
	sa := syscall.SockaddrInet4{
		Addr: addr.As4(),
		Port: int(ap.Port()),
	}
	return sa, nil
}

func addrPortToSockaddrInet6(ap netip.AddrPort) (syscall.SockaddrInet6, error) {
	// ipToSockaddrInet6 has special handling here for zero length slices.
	// We do not, because netip has no concept of a generic zero IP address.
	//
	// addr is allowed to be an IPv4 address, because As16 will convert it
	// to an IPv4-mapped IPv6 address.
	// The error message is kept consistent with ipToSockaddrInet6.
	addr := ap.Addr()
	if !addr.IsValid() {
		return syscall.SockaddrInet6{}, &AddrError{Err: "non-IPv6 address", Addr: addr.String()}
	}
	sa := syscall.SockaddrInet6{
		Addr:   addr.As16(),
		Port:   int(ap.Port()),
		ZoneId: uint32(zoneCache.index(addr.Zone())),
	}
	return sa, nil
}