1 files changed, 179 insertions, 0 deletions
diff --git a/src/net/tcpsock_posix.go b/src/net/tcpsock_posix.go
new file mode 100644
index 0000000..0b3fa1a
--- /dev/null
+++ b/src/net/tcpsock_posix.go
@@ -0,0 +1,179 @@
+// 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"
+	"io"
+	"os"
+	"syscall"
+)
+
+func sockaddrToTCP(sa syscall.Sockaddr) Addr {
+	switch sa := sa.(type) {
+	case *syscall.SockaddrInet4:
+		return &TCPAddr{IP: sa.Addr[0:], Port: sa.Port}
+	case *syscall.SockaddrInet6:
+		return &TCPAddr{IP: sa.Addr[0:], Port: sa.Port, Zone: zoneCache.name(int(sa.ZoneId))}
+	}
+	return nil
+}
+
+func (a *TCPAddr) family() int {
+	if a == nil || len(a.IP) <= IPv4len {
+		return syscall.AF_INET
+	}
+	if a.IP.To4() != nil {
+		return syscall.AF_INET
+	}
+	return syscall.AF_INET6
+}
+
+func (a *TCPAddr) sockaddr(family int) (syscall.Sockaddr, error) {
+	if a == nil {
+		return nil, nil
+	}
+	return ipToSockaddr(family, a.IP, a.Port, a.Zone)
+}
+
+func (a *TCPAddr) toLocal(net string) sockaddr {
+	return &TCPAddr{loopbackIP(net), a.Port, a.Zone}
+}
+
+func (c *TCPConn) readFrom(r io.Reader) (int64, error) {
+	if n, err, handled := splice(c.fd, r); handled {
+		return n, err
+	}
+	if n, err, handled := sendFile(c.fd, r); handled {
+		return n, err
+	}
+	return genericReadFrom(c, r)
+}
+
+func (sd *sysDialer) dialTCP(ctx context.Context, laddr, raddr *TCPAddr) (*TCPConn, error) {
+	if h := sd.testHookDialTCP; h != nil {
+		return h(ctx, sd.network, laddr, raddr)
+	}
+	if h := testHookDialTCP; h != nil {
+		return h(ctx, sd.network, laddr, raddr)
+	}
+	return sd.doDialTCP(ctx, laddr, raddr)
+}
+
+func (sd *sysDialer) doDialTCP(ctx context.Context, laddr, raddr *TCPAddr) (*TCPConn, error) {
+	ctrlCtxFn := sd.Dialer.ControlContext
+	if ctrlCtxFn == nil && sd.Dialer.Control != nil {
+		ctrlCtxFn = func(cxt context.Context, network, address string, c syscall.RawConn) error {
+			return sd.Dialer.Control(network, address, c)
+		}
+	}
+	fd, err := internetSocket(ctx, sd.network, laddr, raddr, syscall.SOCK_STREAM, 0, "dial", ctrlCtxFn)
+
+	// TCP has a rarely used mechanism called a 'simultaneous connection' in
+	// which Dial("tcp", addr1, addr2) run on the machine at addr1 can
+	// connect to a simultaneous Dial("tcp", addr2, addr1) run on the machine
+	// at addr2, without either machine executing Listen. If laddr == nil,
+	// it means we want the kernel to pick an appropriate originating local
+	// address. Some Linux kernels cycle blindly through a fixed range of
+	// local ports, regardless of destination port. If a kernel happens to
+	// pick local port 50001 as the source for a Dial("tcp", "", "localhost:50001"),
+	// then the Dial will succeed, having simultaneously connected to itself.
+	// This can only happen when we are letting the kernel pick a port (laddr == nil)
+	// and when there is no listener for the destination address.
+	// It's hard to argue this is anything other than a kernel bug. If we
+	// see this happen, rather than expose the buggy effect to users, we
+	// close the fd and try again. If it happens twice more, we relent and
+	// use the result. See also:
+	//	https://golang.org/issue/2690
+	//	https://stackoverflow.com/questions/4949858/
+	//
+	// The opposite can also happen: if we ask the kernel to pick an appropriate
+	// originating local address, sometimes it picks one that is already in use.
+	// So if the error is EADDRNOTAVAIL, we have to try again too, just for
+	// a different reason.
+	//
+	// The kernel socket code is no doubt enjoying watching us squirm.
+	for i := 0; i < 2 && (laddr == nil || laddr.Port == 0) && (selfConnect(fd, err) || spuriousENOTAVAIL(err)); i++ {
+		if err == nil {
+			fd.Close()
+		}
+		fd, err = internetSocket(ctx, sd.network, laddr, raddr, syscall.SOCK_STREAM, 0, "dial", ctrlCtxFn)
+	}
+
+	if err != nil {
+		return nil, err
+	}
+	return newTCPConn(fd, sd.Dialer.KeepAlive, testHookSetKeepAlive), nil
+}
+
+func selfConnect(fd *netFD, err error) bool {
+	// If the connect failed, we clearly didn't connect to ourselves.
+	if err != nil {
+		return false
+	}
+
+	// The socket constructor can return an fd with raddr nil under certain
+	// unknown conditions. The errors in the calls there to Getpeername
+	// are discarded, but we can't catch the problem there because those
+	// calls are sometimes legally erroneous with a "socket not connected".
+	// Since this code (selfConnect) is already trying to work around
+	// a problem, we make sure if this happens we recognize trouble and
+	// ask the DialTCP routine to try again.
+	// TODO: try to understand what's really going on.
+	if fd.laddr == nil || fd.raddr == nil {
+		return true
+	}
+	l := fd.laddr.(*TCPAddr)
+	r := fd.raddr.(*TCPAddr)
+	return l.Port == r.Port && l.IP.Equal(r.IP)
+}
+
+func spuriousENOTAVAIL(err error) bool {
+	if op, ok := err.(*OpError); ok {
+		err = op.Err
+	}
+	if sys, ok := err.(*os.SyscallError); ok {
+		err = sys.Err
+	}
+	return err == syscall.EADDRNOTAVAIL
+}
+
+func (ln *TCPListener) ok() bool { return ln != nil && ln.fd != nil }
+
+func (ln *TCPListener) accept() (*TCPConn, error) {
+	fd, err := ln.fd.accept()
+	if err != nil {
+		return nil, err
+	}
+	return newTCPConn(fd, ln.lc.KeepAlive, nil), nil
+}
+
+func (ln *TCPListener) close() error {
+	return ln.fd.Close()
+}
+
+func (ln *TCPListener) file() (*os.File, error) {
+	f, err := ln.fd.dup()
+	if err != nil {
+		return nil, err
+	}
+	return f, nil
+}
+
+func (sl *sysListener) listenTCP(ctx context.Context, laddr *TCPAddr) (*TCPListener, error) {
+	var ctrlCtxFn func(cxt context.Context, network, address string, c syscall.RawConn) error
+	if sl.ListenConfig.Control != nil {
+		ctrlCtxFn = func(cxt context.Context, network, address string, c syscall.RawConn) error {
+			return sl.ListenConfig.Control(network, address, c)
+		}
+	}
+	fd, err := internetSocket(ctx, sl.network, laddr, nil, syscall.SOCK_STREAM, 0, "listen", ctrlCtxFn)
+	if err != nil {
+		return nil, err
+	}
+	return &TCPListener{fd: fd, lc: sl.ListenConfig}, nil
+}