Getting a panic when running tests. For some reason the filter table is

ending up with the wrong chains and is indexing -1 into rules.

4 files changed, 36 insertions, 16 deletions

diff --git a/pkg/tcpip/iptables/BUILD b/pkg/tcpip/iptables/BUILD
index 6ed7c6da0..2893c80cd 100644
--- a/pkg/tcpip/iptables/BUILD
+++ b/pkg/tcpip/iptables/BUILD
@@ -12,6 +12,7 @@ go_library(
     importpath = "gvisor.dev/gvisor/pkg/tcpip/iptables",
     visibility = ["//visibility:public"],
     deps = [
+        "//pkg/log",
         "//pkg/tcpip",
     ],
 )
diff --git a/pkg/tcpip/iptables/iptables.go b/pkg/tcpip/iptables/iptables.go
index 025a4679d..aff8a680b 100644
--- a/pkg/tcpip/iptables/iptables.go
+++ b/pkg/tcpip/iptables/iptables.go
@@ -16,7 +16,12 @@
 // tool.
 package iptables
 
-import "github.com/google/netstack/tcpip"
+import (
+	"fmt"
+
+	"gvisor.dev/gvisor/pkg/log"
+	"gvisor.dev/gvisor/pkg/tcpip"
+)
 
 const (
 	TablenameNat    = "nat"
@@ -135,31 +140,47 @@ func (it *IPTables) Check(hook Hook, pkt tcpip.PacketBuffer) bool {
 
 	// Go through each table containing the hook.
 	for _, tablename := range it.Priorities[hook] {
-		verdict := it.checkTable(tablename)
+		verdict := it.checkTable(hook, pkt, tablename)
 		switch verdict {
-		// TODO: We either got a final verdict or simply continue on.
+		// If the table returns Accept, move on to the next table.
+		case Accept:
+			continue
+		// The Drop verdict is final.
+		case Drop:
+			log.Infof("kevin: Packet dropped")
+			return false
+		case Stolen, Queue, Repeat, None, Jump, Return, Continue:
+			panic(fmt.Sprintf("Unimplemented verdict %v.", verdict))
 		}
 	}
+
+	// Every table returned Accept.
+	log.Infof("kevin: Packet accepted")
+	return true
 }
 
-func (it *IPTables) checkTable(hook Hook, pkt tcpip.PacketBuffer, tablename string) bool {
+func (it *IPTables) checkTable(hook Hook, pkt tcpip.PacketBuffer, tablename string) Verdict {
 	log.Infof("kevin: iptables.IPTables: checking table %q", tablename)
 	table := it.Tables[tablename]
-	ruleIdx := table.BuiltinChains[hook]
+	log.Infof("kevin: iptables.IPTables: table %+v", table)
 
 	// Start from ruleIdx and go down until a rule gives us a verdict.
 	for ruleIdx := table.BuiltinChains[hook]; ruleIdx < len(table.Rules); ruleIdx++ {
-		verdict := checkRule(hook, pkt, table, ruleIdx)
+		verdict := it.checkRule(hook, pkt, table, ruleIdx)
 		switch verdict {
+		// For either of these cases, this table is done with the
+		// packet.
 		case Accept, Drop:
 			return verdict
+		// Continue traversing the rules of the table.
 		case Continue:
 			continue
 		case Stolen, Queue, Repeat, None, Jump, Return:
+			panic(fmt.Sprintf("Unimplemented verdict %v.", verdict))
 		}
 	}
 
-	panic("Traversed past the entire list of iptables rules.")
+	panic(fmt.Sprintf("Traversed past the entire list of iptables rules in table %q.", tablename))
 }
 
 func (it *IPTables) checkRule(hook Hook, pkt tcpip.PacketBuffer, table Table, ruleIdx int) Verdict {
diff --git a/pkg/tcpip/iptables/targets.go b/pkg/tcpip/iptables/targets.go
index 2c3598e3d..cb3ac1aff 100644
--- a/pkg/tcpip/iptables/targets.go
+++ b/pkg/tcpip/iptables/targets.go
@@ -16,13 +16,13 @@
 
 package iptables
 
-import "gvisor.dev/gvisor/pkg/tcpip/buffer"
+import "gvisor.dev/gvisor/pkg/tcpip"
 
 // UnconditionalAcceptTarget accepts all packets.
 type UnconditionalAcceptTarget struct{}
 
 // Action implements Target.Action.
-func (UnconditionalAcceptTarget) Action(packet buffer.VectorisedView) (Verdict, string) {
+func (UnconditionalAcceptTarget) Action(packet tcpip.PacketBuffer) (Verdict, string) {
 	return Accept, ""
 }
 
@@ -30,7 +30,7 @@ func (UnconditionalAcceptTarget) Action(packet buffer.VectorisedView) (Verdict,
 type UnconditionalDropTarget struct{}
 
 // Action implements Target.Action.
-func (UnconditionalDropTarget) Action(packet buffer.VectorisedView) (Verdict, string) {
+func (UnconditionalDropTarget) Action(packet tcpip.PacketBuffer) (Verdict, string) {
 	return Drop, ""
 }
 
@@ -38,6 +38,6 @@ func (UnconditionalDropTarget) Action(packet buffer.VectorisedView) (Verdict, st
 type PanicTarget struct{}
 
 // Actions implements Target.Action.
-func (PanicTarget) Action(packet buffer.VectorisedView) (Verdict, string) {
+func (PanicTarget) Action(packet tcpip.PacketBuffer) (Verdict, string) {
 	panic("PanicTarget triggered.")
 }
diff --git a/pkg/tcpip/iptables/types.go b/pkg/tcpip/iptables/types.go
index 540f8c0b4..9f6906100 100644
--- a/pkg/tcpip/iptables/types.go
+++ b/pkg/tcpip/iptables/types.go
@@ -14,9 +14,7 @@
 
 package iptables
 
-import (
-	"gvisor.dev/gvisor/pkg/tcpip/buffer"
-)
+import "gvisor.dev/gvisor/pkg/tcpip"
 
 // A Hook specifies one of the hooks built into the network stack.
 //
@@ -165,7 +163,7 @@ type Matcher interface {
 	// Match returns whether the packet matches and whether the packet
 	// should be "hotdropped", i.e. dropped immediately. This is usually
 	// used for suspicious packets.
-	Match(hook Hook, packet buffer.VectorisedView, interfaceName string) (matches bool, hotdrop bool)
+	Match(hook Hook, packet tcpip.PacketBuffer, interfaceName string) (matches bool, hotdrop bool)
 }
 
 // A Target is the interface for taking an action for a packet.
@@ -173,5 +171,5 @@ type Target interface {
 	// Action takes an action on the packet and returns a verdict on how
 	// traversal should (or should not) continue. If the return value is
 	// Jump, it also returns the name of the chain to jump to.
-	Action(packet buffer.VectorisedView) (Verdict, string)
+	Action(packet tcpip.PacketBuffer) (Verdict, string)
 }