From 7c1587e3401a010d1865df61dbaf117c77dd062e Mon Sep 17 00:00:00 2001
From: Ian Gudger <igudger@google.com>
Date: Mon, 7 Oct 2019 19:28:26 -0700
Subject: Implement IP_TTL.

Also change the default TTL to 64 to match Linux.

PiperOrigin-RevId: 273430341
---
 pkg/sentry/socket/netstack/netstack.go | 40 +++++++++++++++++++++++++++++++---
 1 file changed, 37 insertions(+), 3 deletions(-)

(limited to 'pkg/sentry/socket/netstack/netstack.go')

diff --git a/pkg/sentry/socket/netstack/netstack.go b/pkg/sentry/socket/netstack/netstack.go
index 48f5c6f30..b3546471e 100644
--- a/pkg/sentry/socket/netstack/netstack.go
+++ b/pkg/sentry/socket/netstack/netstack.go
@@ -174,6 +174,10 @@ var Metrics = tcpip.Stats{
 	},
 }
 
+// DefaultTTL is linux's default TTL. All network protocols in all stacks used
+// with this package must have this value set as their default TTL.
+const DefaultTTL = 64
+
 const sizeOfInt32 int = 4
 
 var errStackType = syserr.New("expected but did not receive a netstack.Stack", linux.EINVAL)
@@ -833,7 +837,7 @@ func GetSockOpt(t *kernel.Task, s socket.Socket, ep commonEndpoint, family int,
 		return getSockOptIPv6(t, ep, name, outLen)
 
 	case linux.SOL_IP:
-		return getSockOptIP(t, ep, name, outLen)
+		return getSockOptIP(t, ep, name, outLen, family)
 
 	case linux.SOL_UDP,
 		linux.SOL_ICMPV6,
@@ -1176,8 +1180,25 @@ func getSockOptIPv6(t *kernel.Task, ep commonEndpoint, name, outLen int) (interf
 }
 
 // getSockOptIP implements GetSockOpt when level is SOL_IP.
-func getSockOptIP(t *kernel.Task, ep commonEndpoint, name, outLen int) (interface{}, *syserr.Error) {
+func getSockOptIP(t *kernel.Task, ep commonEndpoint, name, outLen int, family int) (interface{}, *syserr.Error) {
 	switch name {
+	case linux.IP_TTL:
+		if outLen < sizeOfInt32 {
+			return nil, syserr.ErrInvalidArgument
+		}
+
+		var v tcpip.TTLOption
+		if err := ep.GetSockOpt(&v); err != nil {
+			return nil, syserr.TranslateNetstackError(err)
+		}
+
+		// Fill in the default value, if needed.
+		if v == 0 {
+			v = DefaultTTL
+		}
+
+		return int32(v), nil
+
 	case linux.IP_MULTICAST_TTL:
 		if outLen < sizeOfInt32 {
 			return nil, syserr.ErrInvalidArgument
@@ -1648,6 +1669,20 @@ func setSockOptIP(t *kernel.Task, ep commonEndpoint, name int, optVal []byte) *s
 		t.Kernel().EmitUnimplementedEvent(t)
 		return syserr.ErrInvalidArgument
 
+	case linux.IP_TTL:
+		v, err := parseIntOrChar(optVal)
+		if err != nil {
+			return err
+		}
+
+		// -1 means default TTL.
+		if v == -1 {
+			v = 0
+		} else if v < 1 || v > 255 {
+			return syserr.ErrInvalidArgument
+		}
+		return syserr.TranslateNetstackError(ep.SetSockOpt(tcpip.TTLOption(v)))
+
 	case linux.IP_ADD_SOURCE_MEMBERSHIP,
 		linux.IP_BIND_ADDRESS_NO_PORT,
 		linux.IP_BLOCK_SOURCE,
@@ -1673,7 +1708,6 @@ func setSockOptIP(t *kernel.Task, ep commonEndpoint, name int, optVal []byte) *s
 		linux.IP_RETOPTS,
 		linux.IP_TOS,
 		linux.IP_TRANSPARENT,
-		linux.IP_TTL,
 		linux.IP_UNBLOCK_SOURCE,
 		linux.IP_UNICAST_IF,
 		linux.IP_XFRM_POLICY,
-- 
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