net: enable fast socket creation with close-on-exec flag on freebsd

Also makes variable names explicit.

Fixes #7186.

LGTM=iant
R=golang-codereviews, gobot, iant, bradfitz
CC=golang-codereviews
https://golang.org/cl/69100043

src/pkg/net/sock_cloexec.go

@@ -5,7 +5,7 @@
 // This file implements sysSocket and accept for platforms that
 // provide a fast path for setting SetNonblock and CloseOnExec.
 
-// +build linux
+// +build freebsd linux
 
 package net
 
@@ -13,18 +13,20 @@ import "syscall"
 
 // Wrapper around the socket system call that marks the returned file
 // descriptor as nonblocking and close-on-exec.
-func sysSocket(f, t, p int) (int, error) {
-	s, err := syscall.Socket(f, t|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, p)
-	// The SOCK_NONBLOCK and SOCK_CLOEXEC flags were introduced in
-	// Linux 2.6.27.  If we get an EINVAL error, fall back to
-	// using socket without them.
-	if err == nil || err != syscall.EINVAL {
+func sysSocket(family, sotype, proto int) (int, error) {
+	s, err := syscall.Socket(family, sotype|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, proto)
+	// On Linux the SOCK_NONBLOCK and SOCK_CLOEXEC flags were
+	// introduced in 2.6.27 kernel and on FreeBSD both flags were
+	// introduced in 10 kernel. If we get an EINVAL error on Linux
+	// or EPROTONOSUPPORT error on FreeBSD, fall back to using
+	// socket without them.
+	if err == nil || (err != syscall.EPROTONOSUPPORT && err != syscall.EINVAL) {
 		return s, err
 	}
 
 	// See ../syscall/exec_unix.go for description of ForkLock.
 	syscall.ForkLock.RLock()
-	s, err = syscall.Socket(f, t, p)
+	s, err = syscall.Socket(family, sotype, proto)
 	if err == nil {
 		syscall.CloseOnExec(s)
 	}
@@ -41,12 +43,14 @@ func sysSocket(f, t, p int) (int, error) {
 
 // Wrapper around the accept system call that marks the returned file
 // descriptor as nonblocking and close-on-exec.
-func accept(fd int) (int, syscall.Sockaddr, error) {
-	nfd, sa, err := syscall.Accept4(fd, syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC)
-	// The accept4 system call was introduced in Linux 2.6.28.  If
-	// we get an ENOSYS or EINVAL error, fall back to using accept.
+func accept(s int) (int, syscall.Sockaddr, error) {
+	ns, sa, err := syscall.Accept4(s, syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC)
+	// On Linux the accept4 system call was introduced in 2.6.28
+	// kernel and on FreeBSD it was introduced in 10 kernel. If we
+	// get an ENOSYS error on both Linux and FreeBSD, or EINVAL
+	// error on Linux, fall back to using accept.
 	if err == nil || (err != syscall.ENOSYS && err != syscall.EINVAL) {
-		return nfd, sa, err
+		return ns, sa, err
 	}
 
 	// See ../syscall/exec_unix.go for description of ForkLock.
@@ -54,16 +58,16 @@ func accept(fd int) (int, syscall.Sockaddr, error) {
 	// because we have put fd.sysfd into non-blocking mode.
 	// However, a call to the File method will put it back into
 	// blocking mode. We can't take that risk, so no use of ForkLock here.
-	nfd, sa, err = syscall.Accept(fd)
+	ns, sa, err = syscall.Accept(s)
 	if err == nil {
-		syscall.CloseOnExec(nfd)
+		syscall.CloseOnExec(ns)
 	}
 	if err != nil {
 		return -1, nil, err
 	}
-	if err = syscall.SetNonblock(nfd, true); err != nil {
-		syscall.Close(nfd)
+	if err = syscall.SetNonblock(ns, true); err != nil {
+		syscall.Close(ns)
 		return -1, nil, err
 	}
-	return nfd, sa, nil
+	return ns, sa, nil
 }

src/pkg/net/sys_cloexec.go

@@ -5,7 +5,7 @@
 // This file implements sysSocket and accept for platforms that do not
 // provide a fast path for setting SetNonblock and CloseOnExec.
 
-// +build darwin dragonfly freebsd nacl netbsd openbsd solaris
+// +build darwin dragonfly nacl netbsd openbsd solaris
 
 package net
 
@@ -13,10 +13,10 @@ import "syscall"
 
 // Wrapper around the socket system call that marks the returned file
 // descriptor as nonblocking and close-on-exec.
-func sysSocket(f, t, p int) (int, error) {
+func sysSocket(family, sotype, proto int) (int, error) {
 	// See ../syscall/exec_unix.go for description of ForkLock.
 	syscall.ForkLock.RLock()
-	s, err := syscall.Socket(f, t, p)
+	s, err := syscall.Socket(family, sotype, proto)
 	if err == nil {
 		syscall.CloseOnExec(s)
 	}
@@ -33,22 +33,22 @@ func sysSocket(f, t, p int) (int, error) {
 
 // Wrapper around the accept system call that marks the returned file
 // descriptor as nonblocking and close-on-exec.
-func accept(fd int) (int, syscall.Sockaddr, error) {
+func accept(s int) (int, syscall.Sockaddr, error) {
 	// See ../syscall/exec_unix.go for description of ForkLock.
 	// It is probably okay to hold the lock across syscall.Accept
 	// because we have put fd.sysfd into non-blocking mode.
 	// However, a call to the File method will put it back into
 	// blocking mode. We can't take that risk, so no use of ForkLock here.
-	nfd, sa, err := syscall.Accept(fd)
+	ns, sa, err := syscall.Accept(s)
 	if err == nil {
-		syscall.CloseOnExec(nfd)
+		syscall.CloseOnExec(ns)
 	}
 	if err != nil {
 		return -1, nil, err
 	}
-	if err = syscall.SetNonblock(nfd, true); err != nil {
-		syscall.Close(nfd)
+	if err = syscall.SetNonblock(ns, true); err != nil {
+		syscall.Close(ns)
 		return -1, nil, err
 	}
-	return nfd, sa, nil
+	return ns, sa, nil
 }