1 files changed, 412 insertions, 0 deletions
diff --git a/src/net/cgo_unix.go b/src/net/cgo_unix.go
new file mode 100644
index 0000000..6a2c369
--- /dev/null
+++ b/src/net/cgo_unix.go
@@ -0,0 +1,412 @@
+// Copyright 2011 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.
+
+// This file is called cgo_unix.go, but to allow syscalls-to-libc-based
+// implementations to share the code, it does not use cgo directly.
+// Instead of C.foo it uses _C_foo, which is defined in either
+// cgo_unix_cgo.go or cgo_unix_syscall.go
+
+//go:build !netgo && ((cgo && unix) || darwin)
+
+package net
+
+import (
+	"context"
+	"errors"
+	"syscall"
+	"unsafe"
+
+	"golang.org/x/net/dns/dnsmessage"
+)
+
+// An addrinfoErrno represents a getaddrinfo, getnameinfo-specific
+// error number. It's a signed number and a zero value is a non-error
+// by convention.
+type addrinfoErrno int
+
+func (eai addrinfoErrno) Error() string   { return _C_gai_strerror(_C_int(eai)) }
+func (eai addrinfoErrno) Temporary() bool { return eai == _C_EAI_AGAIN }
+func (eai addrinfoErrno) Timeout() bool   { return false }
+
+type portLookupResult struct {
+	port int
+	err  error
+}
+
+type ipLookupResult struct {
+	addrs []IPAddr
+	cname string
+	err   error
+}
+
+type reverseLookupResult struct {
+	names []string
+	err   error
+}
+
+func cgoLookupHost(ctx context.Context, name string) (hosts []string, err error, completed bool) {
+	addrs, err, completed := cgoLookupIP(ctx, "ip", name)
+	for _, addr := range addrs {
+		hosts = append(hosts, addr.String())
+	}
+	return
+}
+
+func cgoLookupPort(ctx context.Context, network, service string) (port int, err error, completed bool) {
+	var hints _C_struct_addrinfo
+	switch network {
+	case "": // no hints
+	case "tcp", "tcp4", "tcp6":
+		*_C_ai_socktype(&hints) = _C_SOCK_STREAM
+		*_C_ai_protocol(&hints) = _C_IPPROTO_TCP
+	case "udp", "udp4", "udp6":
+		*_C_ai_socktype(&hints) = _C_SOCK_DGRAM
+		*_C_ai_protocol(&hints) = _C_IPPROTO_UDP
+	default:
+		return 0, &DNSError{Err: "unknown network", Name: network + "/" + service}, true
+	}
+	switch ipVersion(network) {
+	case '4':
+		*_C_ai_family(&hints) = _C_AF_INET
+	case '6':
+		*_C_ai_family(&hints) = _C_AF_INET6
+	}
+	if ctx.Done() == nil {
+		port, err := cgoLookupServicePort(&hints, network, service)
+		return port, err, true
+	}
+	result := make(chan portLookupResult, 1)
+	go cgoPortLookup(result, &hints, network, service)
+	select {
+	case r := <-result:
+		return r.port, r.err, true
+	case <-ctx.Done():
+		// Since there isn't a portable way to cancel the lookup,
+		// we just let it finish and write to the buffered channel.
+		return 0, mapErr(ctx.Err()), false
+	}
+}
+
+func cgoLookupServicePort(hints *_C_struct_addrinfo, network, service string) (port int, err error) {
+	cservice := make([]byte, len(service)+1)
+	copy(cservice, service)
+	// Lowercase the C service name.
+	for i, b := range cservice[:len(service)] {
+		cservice[i] = lowerASCII(b)
+	}
+	var res *_C_struct_addrinfo
+	gerrno, err := _C_getaddrinfo(nil, (*_C_char)(unsafe.Pointer(&cservice[0])), hints, &res)
+	if gerrno != 0 {
+		isTemporary := false
+		switch gerrno {
+		case _C_EAI_SYSTEM:
+			if err == nil { // see golang.org/issue/6232
+				err = syscall.EMFILE
+			}
+		default:
+			err = addrinfoErrno(gerrno)
+			isTemporary = addrinfoErrno(gerrno).Temporary()
+		}
+		return 0, &DNSError{Err: err.Error(), Name: network + "/" + service, IsTemporary: isTemporary}
+	}
+	defer _C_freeaddrinfo(res)
+
+	for r := res; r != nil; r = *_C_ai_next(r) {
+		switch *_C_ai_family(r) {
+		case _C_AF_INET:
+			sa := (*syscall.RawSockaddrInet4)(unsafe.Pointer(*_C_ai_addr(r)))
+			p := (*[2]byte)(unsafe.Pointer(&sa.Port))
+			return int(p[0])<<8 | int(p[1]), nil
+		case _C_AF_INET6:
+			sa := (*syscall.RawSockaddrInet6)(unsafe.Pointer(*_C_ai_addr(r)))
+			p := (*[2]byte)(unsafe.Pointer(&sa.Port))
+			return int(p[0])<<8 | int(p[1]), nil
+		}
+	}
+	return 0, &DNSError{Err: "unknown port", Name: network + "/" + service}
+}
+
+func cgoPortLookup(result chan<- portLookupResult, hints *_C_struct_addrinfo, network, service string) {
+	port, err := cgoLookupServicePort(hints, network, service)
+	result <- portLookupResult{port, err}
+}
+
+func cgoLookupIPCNAME(network, name string) (addrs []IPAddr, cname string, err error) {
+	acquireThread()
+	defer releaseThread()
+
+	var hints _C_struct_addrinfo
+	*_C_ai_flags(&hints) = cgoAddrInfoFlags
+	*_C_ai_socktype(&hints) = _C_SOCK_STREAM
+	*_C_ai_family(&hints) = _C_AF_UNSPEC
+	switch ipVersion(network) {
+	case '4':
+		*_C_ai_family(&hints) = _C_AF_INET
+	case '6':
+		*_C_ai_family(&hints) = _C_AF_INET6
+	}
+
+	h := make([]byte, len(name)+1)
+	copy(h, name)
+	var res *_C_struct_addrinfo
+	gerrno, err := _C_getaddrinfo((*_C_char)(unsafe.Pointer(&h[0])), nil, &hints, &res)
+	if gerrno != 0 {
+		isErrorNoSuchHost := false
+		isTemporary := false
+		switch gerrno {
+		case _C_EAI_SYSTEM:
+			if err == nil {
+				// err should not be nil, but sometimes getaddrinfo returns
+				// gerrno == _C_EAI_SYSTEM with err == nil on Linux.
+				// The report claims that it happens when we have too many
+				// open files, so use syscall.EMFILE (too many open files in system).
+				// Most system calls would return ENFILE (too many open files),
+				// so at the least EMFILE should be easy to recognize if this
+				// comes up again. golang.org/issue/6232.
+				err = syscall.EMFILE
+			}
+		case _C_EAI_NONAME:
+			err = errNoSuchHost
+			isErrorNoSuchHost = true
+		default:
+			err = addrinfoErrno(gerrno)
+			isTemporary = addrinfoErrno(gerrno).Temporary()
+		}
+
+		return nil, "", &DNSError{Err: err.Error(), Name: name, IsNotFound: isErrorNoSuchHost, IsTemporary: isTemporary}
+	}
+	defer _C_freeaddrinfo(res)
+
+	if res != nil {
+		cname = _C_GoString(*_C_ai_canonname(res))
+		if cname == "" {
+			cname = name
+		}
+		if len(cname) > 0 && cname[len(cname)-1] != '.' {
+			cname += "."
+		}
+	}
+	for r := res; r != nil; r = *_C_ai_next(r) {
+		// We only asked for SOCK_STREAM, but check anyhow.
+		if *_C_ai_socktype(r) != _C_SOCK_STREAM {
+			continue
+		}
+		switch *_C_ai_family(r) {
+		case _C_AF_INET:
+			sa := (*syscall.RawSockaddrInet4)(unsafe.Pointer(*_C_ai_addr(r)))
+			addr := IPAddr{IP: copyIP(sa.Addr[:])}
+			addrs = append(addrs, addr)
+		case _C_AF_INET6:
+			sa := (*syscall.RawSockaddrInet6)(unsafe.Pointer(*_C_ai_addr(r)))
+			addr := IPAddr{IP: copyIP(sa.Addr[:]), Zone: zoneCache.name(int(sa.Scope_id))}
+			addrs = append(addrs, addr)
+		}
+	}
+	return addrs, cname, nil
+}
+
+func cgoIPLookup(result chan<- ipLookupResult, network, name string) {
+	addrs, cname, err := cgoLookupIPCNAME(network, name)
+	result <- ipLookupResult{addrs, cname, err}
+}
+
+func cgoLookupIP(ctx context.Context, network, name string) (addrs []IPAddr, err error, completed bool) {
+	if ctx.Done() == nil {
+		addrs, _, err = cgoLookupIPCNAME(network, name)
+		return addrs, err, true
+	}
+	result := make(chan ipLookupResult, 1)
+	go cgoIPLookup(result, network, name)
+	select {
+	case r := <-result:
+		return r.addrs, r.err, true
+	case <-ctx.Done():
+		return nil, mapErr(ctx.Err()), false
+	}
+}
+
+// These are roughly enough for the following:
+//
+//	 Source		Encoding			Maximum length of single name entry
+//	 Unicast DNS		ASCII or			<=253 + a NUL terminator
+//				Unicode in RFC 5892		252 * total number of labels + delimiters + a NUL terminator
+//	 Multicast DNS	UTF-8 in RFC 5198 or		<=253 + a NUL terminator
+//				the same as unicast DNS ASCII	<=253 + a NUL terminator
+//	 Local database	various				depends on implementation
+const (
+	nameinfoLen    = 64
+	maxNameinfoLen = 4096
+)
+
+func cgoLookupPTR(ctx context.Context, addr string) (names []string, err error, completed bool) {
+	var zone string
+	ip := parseIPv4(addr)
+	if ip == nil {
+		ip, zone = parseIPv6Zone(addr)
+	}
+	if ip == nil {
+		return nil, &DNSError{Err: "invalid address", Name: addr}, true
+	}
+	sa, salen := cgoSockaddr(ip, zone)
+	if sa == nil {
+		return nil, &DNSError{Err: "invalid address " + ip.String(), Name: addr}, true
+	}
+	if ctx.Done() == nil {
+		names, err := cgoLookupAddrPTR(addr, sa, salen)
+		return names, err, true
+	}
+	result := make(chan reverseLookupResult, 1)
+	go cgoReverseLookup(result, addr, sa, salen)
+	select {
+	case r := <-result:
+		return r.names, r.err, true
+	case <-ctx.Done():
+		return nil, mapErr(ctx.Err()), false
+	}
+}
+
+func cgoLookupAddrPTR(addr string, sa *_C_struct_sockaddr, salen _C_socklen_t) (names []string, err error) {
+	acquireThread()
+	defer releaseThread()
+
+	var gerrno int
+	var b []byte
+	for l := nameinfoLen; l <= maxNameinfoLen; l *= 2 {
+		b = make([]byte, l)
+		gerrno, err = cgoNameinfoPTR(b, sa, salen)
+		if gerrno == 0 || gerrno != _C_EAI_OVERFLOW {
+			break
+		}
+	}
+	if gerrno != 0 {
+		isTemporary := false
+		switch gerrno {
+		case _C_EAI_SYSTEM:
+			if err == nil { // see golang.org/issue/6232
+				err = syscall.EMFILE
+			}
+		default:
+			err = addrinfoErrno(gerrno)
+			isTemporary = addrinfoErrno(gerrno).Temporary()
+		}
+		return nil, &DNSError{Err: err.Error(), Name: addr, IsTemporary: isTemporary}
+	}
+	for i := 0; i < len(b); i++ {
+		if b[i] == 0 {
+			b = b[:i]
+			break
+		}
+	}
+	return []string{absDomainName(string(b))}, nil
+}
+
+func cgoReverseLookup(result chan<- reverseLookupResult, addr string, sa *_C_struct_sockaddr, salen _C_socklen_t) {
+	names, err := cgoLookupAddrPTR(addr, sa, salen)
+	result <- reverseLookupResult{names, err}
+}
+
+func cgoSockaddr(ip IP, zone string) (*_C_struct_sockaddr, _C_socklen_t) {
+	if ip4 := ip.To4(); ip4 != nil {
+		return cgoSockaddrInet4(ip4), _C_socklen_t(syscall.SizeofSockaddrInet4)
+	}
+	if ip6 := ip.To16(); ip6 != nil {
+		return cgoSockaddrInet6(ip6, zoneCache.index(zone)), _C_socklen_t(syscall.SizeofSockaddrInet6)
+	}
+	return nil, 0
+}
+
+func cgoLookupCNAME(ctx context.Context, name string) (cname string, err error, completed bool) {
+	resources, err := resSearch(ctx, name, int(dnsmessage.TypeCNAME), int(dnsmessage.ClassINET))
+	if err != nil {
+		return
+	}
+	cname, err = parseCNAMEFromResources(resources)
+	if err != nil {
+		return "", err, false
+	}
+	return cname, nil, true
+}
+
+// resSearch will make a call to the 'res_nsearch' routine in the C library
+// and parse the output as a slice of DNS resources.
+func resSearch(ctx context.Context, hostname string, rtype, class int) ([]dnsmessage.Resource, error) {
+	if ctx.Done() == nil {
+		return cgoResSearch(hostname, rtype, class)
+	}
+
+	type result struct {
+		res []dnsmessage.Resource
+		err error
+	}
+
+	res := make(chan result, 1)
+	go func() {
+		r, err := cgoResSearch(hostname, rtype, class)
+		res <- result{
+			res: r,
+			err: err,
+		}
+	}()
+
+	select {
+	case res := <-res:
+		return res.res, res.err
+	case <-ctx.Done():
+		return nil, mapErr(ctx.Err())
+	}
+}
+
+func cgoResSearch(hostname string, rtype, class int) ([]dnsmessage.Resource, error) {
+	acquireThread()
+	defer releaseThread()
+
+	state := (*_C_struct___res_state)(_C_malloc(unsafe.Sizeof(_C_struct___res_state{})))
+	defer _C_free(unsafe.Pointer(state))
+	if err := _C_res_ninit(state); err != nil {
+		return nil, errors.New("res_ninit failure: " + err.Error())
+	}
+	defer _C_res_nclose(state)
+
+	// Some res_nsearch implementations (like macOS) do not set errno.
+	// They set h_errno, which is not per-thread and useless to us.
+	// res_nsearch returns the size of the DNS response packet.
+	// But if the DNS response packet contains failure-like response codes,
+	// res_search returns -1 even though it has copied the packet into buf,
+	// giving us no way to find out how big the packet is.
+	// For now, we are willing to take res_search's word that there's nothing
+	// useful in the response, even though there *is* a response.
+	bufSize := maxDNSPacketSize
+	buf := (*_C_uchar)(_C_malloc(uintptr(bufSize)))
+	defer _C_free(unsafe.Pointer(buf))
+
+	s := _C_CString(hostname)
+	defer _C_FreeCString(s)
+
+	var size int
+	for {
+		size, _ = _C_res_nsearch(state, s, class, rtype, buf, bufSize)
+		if size <= 0 || size > 0xffff {
+			return nil, errors.New("res_nsearch failure")
+		}
+		if size <= bufSize {
+			break
+		}
+
+		// Allocate a bigger buffer to fit the entire msg.
+		_C_free(unsafe.Pointer(buf))
+		bufSize = size
+		buf = (*_C_uchar)(_C_malloc(uintptr(bufSize)))
+	}
+
+	var p dnsmessage.Parser
+	if _, err := p.Start(unsafe.Slice((*byte)(unsafe.Pointer(buf)), size)); err != nil {
+		return nil, err
+	}
+	p.SkipAllQuestions()
+	resources, err := p.AllAnswers()
+	if err != nil {
+		return nil, err
+	}
+	return resources, nil
+}