4 files changed, 88 insertions, 11 deletions

diff --git a/pkg/tcpip/iptables/BUILD b/pkg/tcpip/iptables/BUILD
index 64769c333..2893c80cd 100644
--- a/pkg/tcpip/iptables/BUILD
+++ b/pkg/tcpip/iptables/BUILD
@@ -13,6 +13,6 @@ go_library(
     visibility = ["//visibility:public"],
     deps = [
         "//pkg/log",
-        "//pkg/tcpip/buffer",
+        "//pkg/tcpip",
     ],
 )
diff --git a/pkg/tcpip/iptables/iptables.go b/pkg/tcpip/iptables/iptables.go
index db0450a21..91abbbea8 100644
--- a/pkg/tcpip/iptables/iptables.go
+++ b/pkg/tcpip/iptables/iptables.go
@@ -16,6 +16,13 @@
 // tool.
 package iptables
 
+import (
+	"fmt"
+
+	"gvisor.dev/gvisor/pkg/log"
+	"gvisor.dev/gvisor/pkg/tcpip"
+)
+
 const (
 	TablenameNat    = "nat"
 	TablenameMangle = "mangle"
@@ -121,3 +128,76 @@ func EmptyFilterTable() Table {
 		UserChains: map[string]int{},
 	}
 }
+
+// Check runs pkt through the rules for hook. It returns true when the packet
+// should continue traversing the network stack and false when it should be
+// dropped.
+func (it *IPTables) Check(hook Hook, pkt tcpip.PacketBuffer) bool {
+	// TODO(gvisor.dev/issue/170): A lot of this is uncomplicated because
+	// we're missing features. Jumps, the call stack, etc. aren't checked
+	// for yet because we're yet to support them.
+	log.Infof("kevin: iptables.IPTables: checking hook %v", hook)
+
+	// Go through each table containing the hook.
+	for _, tablename := range it.Priorities[hook] {
+		verdict := it.checkTable(hook, pkt, tablename)
+		switch verdict {
+		// 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) Verdict {
+	log.Infof("kevin: iptables.IPTables: checking table %q", tablename)
+	table := it.Tables[tablename]
+	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 := 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(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 {
+	rule := table.Rules[ruleIdx]
+	// Go through each rule matcher. If they all match, run
+	// the rule target.
+	for _, matcher := range rule.Matchers {
+		matches, hotdrop := matcher.Match(hook, pkt, "")
+		if hotdrop {
+			return Drop
+		}
+		if !matches {
+			return Continue
+		}
+	}
+
+	// All the matchers matched, so run the target.
+	verdict, _ := rule.Target.Action(pkt)
+	return verdict
+}
diff --git a/pkg/tcpip/iptables/targets.go b/pkg/tcpip/iptables/targets.go
index d65ed8df5..8180dcefd 100644
--- a/pkg/tcpip/iptables/targets.go
+++ b/pkg/tcpip/iptables/targets.go
@@ -18,14 +18,14 @@ package iptables
 
 import (
 	"gvisor.dev/gvisor/pkg/log"
-	"gvisor.dev/gvisor/pkg/tcpip/buffer"
+	"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, ""
 }
 
@@ -33,7 +33,7 @@ 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, ""
 }
 
@@ -42,8 +42,7 @@ func (UnconditionalDropTarget) Action(packet buffer.VectorisedView) (Verdict, st
 type ErrorTarget struct{}
 
 // Actions implements Target.Action.
-func (ErrorTarget) Action(packet buffer.VectorisedView) (Verdict, string) {
+func (ErrorTarget) Action(packet tcpip.PacketBuffer) (Verdict, string) {
 	log.Warningf("ErrorTarget triggered.")
 	return Drop, ""
-
 }
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)
 }