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//go:build unix || js || wasip1 || windows 6 7package net 8 9import ( 10 "context" 11 "internal/poll" 12 "net/netip" 13 "runtime" 14 "syscall" 15 _ "unsafe" // for linkname 16) 17 18// probe probes IPv4, IPv6 and IPv4-mapped IPv6 communication 19// capabilities which are controlled by the IPV6_V6ONLY socket option 20// and kernel configuration. 21// 22// Should we try to use the IPv4 socket interface if we're only 23// dealing with IPv4 sockets? As long as the host system understands 24// IPv4-mapped IPv6, it's okay to pass IPv4-mapped IPv6 addresses to 25// the IPv6 interface. That simplifies our code and is most 26// general. Unfortunately, we need to run on kernels built without 27// IPv6 support too. So probe the kernel to figure it out. 28func (p *ipStackCapabilities) probe() { 29 switch runtime.GOOS { 30 case "js", "wasip1": 31 // Both ipv4 and ipv6 are faked; see net_fake.go. 32 p.ipv4Enabled = true 33 p.ipv6Enabled = true 34 p.ipv4MappedIPv6Enabled = true 35 return 36 } 37 38 s, err := sysSocket(syscall.AF_INET, syscall.SOCK_STREAM, syscall.IPPROTO_TCP) 39 switch err { 40 case syscall.EAFNOSUPPORT, syscall.EPROTONOSUPPORT: 41 case nil: 42 poll.CloseFunc(s) 43 p.ipv4Enabled = true 44 } 45 var probes = []struct { 46 laddr TCPAddr 47 value int 48 }{ 49 // IPv6 communication capability 50 {laddr: TCPAddr{IP: ParseIP("::1")}, value: 1}, 51 // IPv4-mapped IPv6 address communication capability 52 {laddr: TCPAddr{IP: IPv4(127, 0, 0, 1)}, value: 0}, 53 } 54 switch runtime.GOOS { 55 case "dragonfly", "openbsd": 56 // The latest DragonFly BSD and OpenBSD kernels don't 57 // support IPV6_V6ONLY=0. They always return an error 58 // and we don't need to probe the capability. 59 probes = probes[:1] 60 } 61 for i := range probes { 62 s, err := sysSocket(syscall.AF_INET6, syscall.SOCK_STREAM, syscall.IPPROTO_TCP) 63 if err != nil { 64 continue 65 } 66 defer poll.CloseFunc(s) 67 syscall.SetsockoptInt(s, syscall.IPPROTO_IPV6, syscall.IPV6_V6ONLY, probes[i].value) 68 sa, err := probes[i].laddr.sockaddr(syscall.AF_INET6) 69 if err != nil { 70 continue 71 } 72 if err := syscall.Bind(s, sa); err != nil { 73 continue 74 } 75 if i == 0 { 76 p.ipv6Enabled = true 77 } else { 78 p.ipv4MappedIPv6Enabled = true 79 } 80 } 81} 82 83// favoriteAddrFamily returns the appropriate address family for the 84// given network, laddr, raddr and mode. 85// 86// If mode indicates "listen" and laddr is a wildcard, we assume that 87// the user wants to make a passive-open connection with a wildcard 88// address family, both AF_INET and AF_INET6, and a wildcard address 89// like the following: 90// 91// - A listen for a wildcard communication domain, "tcp" or 92// "udp", with a wildcard address: If the platform supports 93// both IPv6 and IPv4-mapped IPv6 communication capabilities, 94// or does not support IPv4, we use a dual stack, AF_INET6 and 95// IPV6_V6ONLY=0, wildcard address listen. The dual stack 96// wildcard address listen may fall back to an IPv6-only, 97// AF_INET6 and IPV6_V6ONLY=1, wildcard address listen. 98// Otherwise we prefer an IPv4-only, AF_INET, wildcard address 99// listen. 100// 101// - A listen for a wildcard communication domain, "tcp" or 102// "udp", with an IPv4 wildcard address: same as above. 103// 104// - A listen for a wildcard communication domain, "tcp" or 105// "udp", with an IPv6 wildcard address: same as above. 106// 107// - A listen for an IPv4 communication domain, "tcp4" or "udp4", 108// with an IPv4 wildcard address: We use an IPv4-only, AF_INET, 109// wildcard address listen. 110// 111// - A listen for an IPv6 communication domain, "tcp6" or "udp6", 112// with an IPv6 wildcard address: We use an IPv6-only, AF_INET6 113// and IPV6_V6ONLY=1, wildcard address listen. 114// 115// Otherwise guess: If the addresses are IPv4 then returns AF_INET, 116// or else returns AF_INET6. It also returns a boolean value what 117// designates IPV6_V6ONLY option. 118// 119// Note that the latest DragonFly BSD and OpenBSD kernels allow 120// neither "net.inet6.ip6.v6only=1" change nor IPPROTO_IPV6 level 121// IPV6_V6ONLY socket option setting. 122// 123// favoriteAddrFamily should be an internal detail, 124// but widely used packages access it using linkname. 125// Notable members of the hall of shame include: 126// - github.com/database64128/tfo-go/v2 127// - github.com/metacubex/tfo-go 128// - github.com/sagernet/tfo-go 129// 130// Do not remove or change the type signature. 131// See go.dev/issue/67401. 132// 133//go:linkname favoriteAddrFamily 134func favoriteAddrFamily(network string, laddr, raddr sockaddr, mode string) (family int, ipv6only bool) { 135 switch network[len(network)-1] { 136 case '4': 137 return syscall.AF_INET, false 138 case '6': 139 return syscall.AF_INET6, true 140 } 141 142 if mode == "listen" && (laddr == nil || laddr.isWildcard()) { 143 if supportsIPv4map() || !supportsIPv4() { 144 return syscall.AF_INET6, false 145 } 146 if laddr == nil { 147 return syscall.AF_INET, false 148 } 149 return laddr.family(), false 150 } 151 152 if (laddr == nil || laddr.family() == syscall.AF_INET) && 153 (raddr == nil || raddr.family() == syscall.AF_INET) { 154 return syscall.AF_INET, false 155 } 156 return syscall.AF_INET6, false 157} 158 159func internetSocket(ctx context.Context, net string, laddr, raddr sockaddr, sotype, proto int, mode string, ctrlCtxFn func(context.Context, string, string, syscall.RawConn) error) (fd *netFD, err error) { 160 switch runtime.GOOS { 161 case "aix", "windows", "openbsd", "js", "wasip1": 162 if mode == "dial" && raddr.isWildcard() { 163 raddr = raddr.toLocal(net) 164 } 165 } 166 family, ipv6only := favoriteAddrFamily(net, laddr, raddr, mode) 167 return socket(ctx, net, family, sotype, proto, ipv6only, laddr, raddr, ctrlCtxFn) 168} 169 170func ipToSockaddrInet4(ip IP, port int) (syscall.SockaddrInet4, error) { 171 if len(ip) == 0 { 172 ip = IPv4zero 173 } 174 ip4 := ip.To4() 175 if ip4 == nil { 176 return syscall.SockaddrInet4{}, &AddrError{Err: "non-IPv4 address", Addr: ip.String()} 177 } 178 sa := syscall.SockaddrInet4{Port: port} 179 copy(sa.Addr[:], ip4) 180 return sa, nil 181} 182 183func ipToSockaddrInet6(ip IP, port int, zone string) (syscall.SockaddrInet6, error) { 184 // In general, an IP wildcard address, which is either 185 // "0.0.0.0" or "::", means the entire IP addressing 186 // space. For some historical reason, it is used to 187 // specify "any available address" on some operations 188 // of IP node. 189 // 190 // When the IP node supports IPv4-mapped IPv6 address, 191 // we allow a listener to listen to the wildcard 192 // address of both IP addressing spaces by specifying 193 // IPv6 wildcard address. 194 if len(ip) == 0 || ip.Equal(IPv4zero) { 195 ip = IPv6zero 196 } 197 // We accept any IPv6 address including IPv4-mapped 198 // IPv6 address. 199 ip6 := ip.To16() 200 if ip6 == nil { 201 return syscall.SockaddrInet6{}, &AddrError{Err: "non-IPv6 address", Addr: ip.String()} 202 } 203 sa := syscall.SockaddrInet6{Port: port, ZoneId: uint32(zoneCache.index(zone))} 204 copy(sa.Addr[:], ip6) 205 return sa, nil 206} 207 208// ipToSockaddr should be an internal detail, 209// but widely used packages access it using linkname. 210// Notable members of the hall of shame include: 211// - github.com/database64128/tfo-go/v2 212// - github.com/metacubex/tfo-go 213// - github.com/sagernet/tfo-go 214// 215// Do not remove or change the type signature. 216// See go.dev/issue/67401. 217// 218//go:linkname ipToSockaddr 219func ipToSockaddr(family int, ip IP, port int, zone string) (syscall.Sockaddr, error) { 220 switch family { 221 case syscall.AF_INET: 222 sa, err := ipToSockaddrInet4(ip, port) 223 if err != nil { 224 return nil, err 225 } 226 return &sa, nil 227 case syscall.AF_INET6: 228 sa, err := ipToSockaddrInet6(ip, port, zone) 229 if err != nil { 230 return nil, err 231 } 232 return &sa, nil 233 } 234 return nil, &AddrError{Err: "invalid address family", Addr: ip.String()} 235} 236 237func addrPortToSockaddrInet4(ap netip.AddrPort) (syscall.SockaddrInet4, error) { 238 // ipToSockaddrInet4 has special handling here for zero length slices. 239 // We do not, because netip has no concept of a generic zero IP address. 240 addr := ap.Addr() 241 if !addr.Is4() { 242 return syscall.SockaddrInet4{}, &AddrError{Err: "non-IPv4 address", Addr: addr.String()} 243 } 244 sa := syscall.SockaddrInet4{ 245 Addr: addr.As4(), 246 Port: int(ap.Port()), 247 } 248 return sa, nil 249} 250 251func addrPortToSockaddrInet6(ap netip.AddrPort) (syscall.SockaddrInet6, error) { 252 // ipToSockaddrInet6 has special handling here for zero length slices. 253 // We do not, because netip has no concept of a generic zero IP address. 254 // 255 // addr is allowed to be an IPv4 address, because As16 will convert it 256 // to an IPv4-mapped IPv6 address. 257 // The error message is kept consistent with ipToSockaddrInet6. 258 addr := ap.Addr() 259 if !addr.IsValid() { 260 return syscall.SockaddrInet6{}, &AddrError{Err: "non-IPv6 address", Addr: addr.String()} 261 } 262 sa := syscall.SockaddrInet6{ 263 Addr: addr.As16(), 264 Port: int(ap.Port()), 265 ZoneId: uint32(zoneCache.index(addr.Zone())), 266 } 267 return sa, nil 268} 269