[sys] unix/linux: add ParseOrigDstAddr
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Tobias Klauser (Gerrit)
Oct 25, 2021, 7:29:22 AM10/25/21
to Lorenz Bauer, goph...@pubsubhelper.golang.org, golang-...@googlegroups.com, Go Bot, Ian Lance Taylor, golang-co...@googlegroups.com
Tobias Klauser submitted this change.
Approvals:
Ian Lance Taylor: Looks good to me, approved
Tobias Klauser: Looks good to me, approved; Run TryBots
Go Bot: TryBots succeeded
unix: add ParseOrigDstAddr
Add a function which turns a SocketControlMessage into a Sockaddr.
This can be used with IP(V6)_RECVORIGDSTADDR to retrieve the original
destination address of a packet.
Change-Id: Ib2d80cd01be6642e8b918cbc1584d4a49c3c6f1e
Reviewed-on: https://go-review.googlesource.com/c/sys/+/355609
Reviewed-by: Tobias Klauser <tobias....@gmail.com>
Reviewed-by: Ian Lance Taylor <ia...@golang.org>
Run-TryBot: Tobias Klauser <tobias....@gmail.com>
TryBot-Result: Go Bot <go...@golang.org>
---
M unix/creds_test.go
M unix/sockcmsg_linux.go
2 files changed, 148 insertions(+), 0 deletions(-)
diff --git a/unix/creds_test.go b/unix/creds_test.go
index 1d4c091..9ab57ec 100644
--- a/unix/creds_test.go
+++ b/unix/creds_test.go
@@ -195,3 +195,102 @@
})
}
}
+
+func TestParseOrigDstAddr(t *testing.T) {
+ testcases := []struct {
+ network string
+ address *net.UDPAddr
+ }{
+ {"udp4", &net.UDPAddr{IP: net.IPv4(127, 0, 0, 1)}},
+ {"udp6", &net.UDPAddr{IP: net.IPv6loopback}},
+ }
+
+ for _, test := range testcases {
+ t.Run(test.network, func(t *testing.T) {
+ conn, err := net.ListenUDP(test.network, test.address)
+ if errors.Is(err, unix.EADDRNOTAVAIL) {
+ t.Skipf("%v is not available", test.address)
+ }
+ if err != nil {
+ t.Fatal("Listen:", err)
+ }
+ defer conn.Close()
+
+ raw, err := conn.SyscallConn()
+ if err != nil {
+ t.Fatal("SyscallConn:", err)
+ }
+
+ var opErr error
+ err = raw.Control(func(fd uintptr) {
+ switch test.network {
+ case "udp4":
+ opErr = unix.SetsockoptInt(int(fd), unix.SOL_IP, unix.IP_RECVORIGDSTADDR, 1)
+ case "udp6":
+ opErr = unix.SetsockoptInt(int(fd), unix.SOL_IPV6, unix.IPV6_RECVORIGDSTADDR, 1)
+ }
+ })
+ if err != nil {
+ t.Fatal("Control:", err)
+ }
+ if opErr != nil {
+ t.Fatal("Can't enable RECVORIGDSTADDR:", err)
+ }
+
+ msg := []byte{1}
+ addr := conn.LocalAddr().(*net.UDPAddr)
+ _, err = conn.WriteToUDP(msg, addr)
+ if err != nil {
+ t.Fatal("WriteToUDP:", err)
+ }
+
+ conn.SetReadDeadline(time.Now().Add(100 * time.Millisecond))
+ oob := make([]byte, unix.CmsgSpace(unix.SizeofSockaddrInet6))
+ _, oobn, _, _, err := conn.ReadMsgUDP(msg, oob)
+ if err != nil {
+ t.Fatal("ReadMsgUDP:", err)
+ }
+
+ scms, err := unix.ParseSocketControlMessage(oob[:oobn])
+ if err != nil {
+ t.Fatal("ParseSocketControlMessage:", err)
+ }
+
+ sa, err := unix.ParseOrigDstAddr(&scms[0])
+ if err != nil {
+ t.Fatal("ParseOrigDstAddr:", err)
+ }
+
+ switch test.network {
+ case "udp4":
+ sa4, ok := sa.(*unix.SockaddrInet4)
+ if !ok {
+ t.Fatalf("Got %T not *SockaddrInet4", sa)
+ }
+
+ lo := net.IPv4(127, 0, 0, 1)
+ if addr := net.IP(sa4.Addr[:]); !lo.Equal(addr) {
+ t.Errorf("Got address %v, want %v", addr, lo)
+ }
+
+ if sa4.Port != addr.Port {
+ t.Errorf("Got port %d, want %d", sa4.Port, addr.Port)
+ }
+
+ case "udp6":
+ sa6, ok := sa.(*unix.SockaddrInet6)
+ if !ok {
+ t.Fatalf("Got %T, want *SockaddrInet6", sa)
+ }
+
+ if addr := net.IP(sa6.Addr[:]); !net.IPv6loopback.Equal(addr) {
+ t.Errorf("Got address %v, want %v", addr, net.IPv6loopback)
+ }
+
+ if sa6.Port != addr.Port {
+ t.Errorf("Got port %d, want %d", sa6.Port, addr.Port)
+ }
+ }
+ })
+ }
+}
diff --git a/unix/sockcmsg_linux.go b/unix/sockcmsg_linux.go
index e86d543..326fb04 100644
--- a/unix/sockcmsg_linux.go
+++ b/unix/sockcmsg_linux.go
@@ -56,3 +56,34 @@
*(*Inet6Pktinfo)(h.data(0)) = *info
return b
}
+
+// ParseOrigDstAddr decodes a socket control message containing the original
+// destination address. To receive such a message the IP_RECVORIGDSTADDR or
+// IPV6_RECVORIGDSTADDR option must be enabled on the socket.
+func ParseOrigDstAddr(m *SocketControlMessage) (Sockaddr, error) {
+ switch {
+ case m.Header.Level == SOL_IP && m.Header.Type == IP_ORIGDSTADDR:
+ pp := (*RawSockaddrInet4)(unsafe.Pointer(&m.Data[0]))
+ sa := new(SockaddrInet4)
+ p := (*[2]byte)(unsafe.Pointer(&pp.Port))
+ sa.Port = int(p[0])<<8 + int(p[1])
+ for i := 0; i < len(sa.Addr); i++ {
+ sa.Addr[i] = pp.Addr[i]
+ }
+ return sa, nil
+
+ case m.Header.Level == SOL_IPV6 && m.Header.Type == IPV6_ORIGDSTADDR:
+ pp := (*RawSockaddrInet6)(unsafe.Pointer(&m.Data[0]))
+ sa := new(SockaddrInet6)
+ p := (*[2]byte)(unsafe.Pointer(&pp.Port))
+ sa.Port = int(p[0])<<8 + int(p[1])
+ sa.ZoneId = pp.Scope_id
+ for i := 0; i < len(sa.Addr); i++ {
+ sa.Addr[i] = pp.Addr[i]
+ }
+ return sa, nil
+
+ default:
+ return nil, EINVAL
+ }
+}
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