ipv6: fix multicast socket options on freebsd/386 on amd64

Change-Id: Ifdd525f27a8ed35bda240c08f379014d03fd2201
Reviewed-on: https://go-review.googlesource.com/11226
Reviewed-by: Ian Lance Taylor <iant@golang.org>

2 files changed, 44 insertions, 2 deletions

diff --git a/ipv6/sockopt_ssmreq_unix.go b/ipv6/sockopt_ssmreq_unix.go
index 8e1dcef..c64d6d5 100644
--- a/ipv6/sockopt_ssmreq_unix.go
+++ b/ipv6/sockopt_ssmreq_unix.go
@@ -12,13 +12,28 @@ import (
 	"unsafe"
 )
 
+var freebsd32o64 bool
+
 func setsockoptGroupReq(fd int, opt *sockOpt, ifi *net.Interface, grp net.IP) error {
 	var gr sysGroupReq
 	if ifi != nil {
 		gr.Interface = uint32(ifi.Index)
 	}
 	gr.setGroup(grp)
-	return os.NewSyscallError("setsockopt", setsockopt(fd, opt.level, opt.name, unsafe.Pointer(&gr), sysSizeofGroupReq))
+	var p unsafe.Pointer
+	var l sysSockoptLen
+	if freebsd32o64 {
+		var d [sysSizeofGroupReq + 4]byte
+		s := (*[sysSizeofGroupReq]byte)(unsafe.Pointer(&gr))
+		copy(d[:4], s[:4])
+		copy(d[8:], s[4:])
+		p = unsafe.Pointer(&d[0])
+		l = sysSizeofGroupReq + 4
+	} else {
+		p = unsafe.Pointer(&gr)
+		l = sysSizeofGroupReq
+	}
+	return os.NewSyscallError("setsockopt", setsockopt(fd, opt.level, opt.name, p, l))
 }
 
 func setsockoptGroupSourceReq(fd int, opt *sockOpt, ifi *net.Interface, grp, src net.IP) error {
@@ -27,5 +42,18 @@ func setsockoptGroupSourceReq(fd int, opt *sockOpt, ifi *net.Interface, grp, src
 		gsr.Interface = uint32(ifi.Index)
 	}
 	gsr.setSourceGroup(grp, src)
-	return os.NewSyscallError("setsockopt", setsockopt(fd, opt.level, opt.name, unsafe.Pointer(&gsr), sysSizeofGroupSourceReq))
+	var p unsafe.Pointer
+	var l sysSockoptLen
+	if freebsd32o64 {
+		var d [sysSizeofGroupSourceReq + 4]byte
+		s := (*[sysSizeofGroupSourceReq]byte)(unsafe.Pointer(&gsr))
+		copy(d[:4], s[:4])
+		copy(d[8:], s[4:])
+		p = unsafe.Pointer(&d[0])
+		l = sysSizeofGroupSourceReq + 4
+	} else {
+		p = unsafe.Pointer(&gsr)
+		l = sysSizeofGroupSourceReq
+	}
+	return os.NewSyscallError("setsockopt", setsockopt(fd, opt.level, opt.name, p, l))
 }
diff --git a/ipv6/sys_freebsd.go b/ipv6/sys_freebsd.go
index abf3bb9..feedab0 100644
--- a/ipv6/sys_freebsd.go
+++ b/ipv6/sys_freebsd.go
@@ -6,6 +6,8 @@ package ipv6
 
 import (
 	"net"
+	"runtime"
+	"strings"
 	"syscall"
 	"unsafe"
 
@@ -45,6 +47,18 @@ var (
 	}
 )
 
+func init() {
+	if runtime.GOOS == "freebsd" && runtime.GOARCH == "386" {
+		archs, _ := syscall.Sysctl("kern.supported_archs")
+		for _, s := range strings.Split(archs, " ") {
+			if strings.TrimSpace(s) == "amd64" {
+				freebsd32o64 = true
+				break
+			}
+		}
+	}
+}
+
 func (sa *sysSockaddrInet6) setSockaddr(ip net.IP, i int) {
 	sa.Len = sysSizeofSockaddrInet6
 	sa.Family = syscall.AF_INET6