server: set ttl to 1

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>

1 files changed, 15 insertions, 0 deletions

diff --git a/server/sockopt.go b/server/sockopt.go
index 10b3c186..2392cdf4 100644
--- a/server/sockopt.go
+++ b/server/sockopt.go
@@ -2,6 +2,7 @@ package server
 
 import (
 	"net"
+	"strings"
 	"syscall"
 	"unsafe"
 )
@@ -43,3 +44,17 @@ func SetTcpMD5SigSockopts(fd int, address string, key string) error {
 		uintptr(unsafe.Pointer(&t)), unsafe.Sizeof(t), 0)
 	return e
 }
+
+func SetTcpTTLSockopts(conn *net.TCPConn, ttl int) error {
+	level := syscall.IPPROTO_IP
+	name := syscall.IP_TTL
+	if strings.Contains(conn.RemoteAddr().String(), "[") {
+		level = syscall.IPPROTO_IPV6
+		name = syscall.IPV6_UNICAST_HOPS
+	}
+	file, _ := conn.File()
+	_, _, e := syscall.Syscall6(syscall.SYS_SETSOCKOPT, uintptr(int(file.Fd())),
+		uintptr(level), uintptr(name),
+		uintptr(unsafe.Pointer(&ttl)), unsafe.Sizeof(ttl), 0)
+	return e
+}