net: tweak the ephemeral port range on dragonfly

On DragonFly BSD, we adjust the ephemeral port range because
unlike other BSD systems its default ephemeral port range
doesn't conform to IANA recommendation as described in RFC 6355
and is pretty narrow.

On DragonFly BSD 3.6: default range [1024, 5000], high range [49152, 65535]
On FreeBSD 10: default range [10000, 65535], high range [49152, 65535]
On Linux 3.11: default range [32768, 61000]

Fixes #7541.

LGTM=iant
R=jsing, gobot, iant
CC=golang-codereviews
https://golang.org/cl/80610044

src/pkg/net/sockopt_bsd.go

@@ -8,10 +8,23 @@ package net
 
 import (
 	"os"
+	"runtime"
 	"syscall"
 )
 
 func setDefaultSockopts(s, family, sotype int, ipv6only bool) error {
+	if runtime.GOOS == "dragonfly" && sotype != syscall.SOCK_RAW {
+		// On DragonFly BSD, we adjust the ephemeral port
+		// range because unlike other BSD systems its default
+		// port range doesn't conform to IANA recommendation
+		// as described in RFC 6355 and is pretty narrow.
+		switch family {
+		case syscall.AF_INET:
+			syscall.SetsockoptInt(s, syscall.IPPROTO_IP, syscall.IP_PORTRANGE, syscall.IP_PORTRANGE_HIGH)
+		case syscall.AF_INET6:
+			syscall.SetsockoptInt(s, syscall.IPPROTO_IPV6, syscall.IPV6_PORTRANGE, syscall.IPV6_PORTRANGE_HIGH)
+		}
+	}
 	if family == syscall.AF_INET6 && sotype != syscall.SOCK_RAW {
 		// Allow both IP versions even if the OS default
 		// is otherwise.  Note that some operating systems

src/pkg/syscall/net_nacl.go

@@ -113,9 +113,17 @@ const (
 	SO_KEEPALIVE
 	SO_LINGER
 	SO_ERROR
+	IP_PORTRANGE
+	IP_PORTRANGE_DEFAULT
+	IP_PORTRANGE_LOW
+	IP_PORTRANGE_HIGH
 	IP_MULTICAST_IF
 	IP_MULTICAST_LOOP
 	IP_ADD_MEMBERSHIP
+	IPV6_PORTRANGE
+	IPV6_PORTRANGE_DEFAULT
+	IPV6_PORTRANGE_LOW
+	IPV6_PORTRANGE_HIGH
 	IPV6_MULTICAST_IF
 	IPV6_MULTICAST_LOOP
 	IPV6_JOIN_GROUP