diff options
Diffstat (limited to 'pkg/tcpip/iptables/iptables.go')
| -rw-r--r-- | pkg/tcpip/iptables/iptables.go | 128 |
1 files changed, 90 insertions, 38 deletions
diff --git a/pkg/tcpip/iptables/iptables.go b/pkg/tcpip/iptables/iptables.go index 4bfb3149e..dbaccbb36 100644 --- a/pkg/tcpip/iptables/iptables.go +++ b/pkg/tcpip/iptables/iptables.go @@ -52,10 +52,10 @@ func DefaultTables() IPTables { Tables: map[string]Table{ TablenameNat: Table{ Rules: []Rule{ - Rule{Target: UnconditionalAcceptTarget{}}, - Rule{Target: UnconditionalAcceptTarget{}}, - Rule{Target: UnconditionalAcceptTarget{}}, - Rule{Target: UnconditionalAcceptTarget{}}, + Rule{Target: AcceptTarget{}}, + Rule{Target: AcceptTarget{}}, + Rule{Target: AcceptTarget{}}, + Rule{Target: AcceptTarget{}}, Rule{Target: ErrorTarget{}}, }, BuiltinChains: map[Hook]int{ @@ -74,8 +74,8 @@ func DefaultTables() IPTables { }, TablenameMangle: Table{ Rules: []Rule{ - Rule{Target: UnconditionalAcceptTarget{}}, - Rule{Target: UnconditionalAcceptTarget{}}, + Rule{Target: AcceptTarget{}}, + Rule{Target: AcceptTarget{}}, Rule{Target: ErrorTarget{}}, }, BuiltinChains: map[Hook]int{ @@ -90,9 +90,9 @@ func DefaultTables() IPTables { }, TablenameFilter: Table{ Rules: []Rule{ - Rule{Target: UnconditionalAcceptTarget{}}, - Rule{Target: UnconditionalAcceptTarget{}}, - Rule{Target: UnconditionalAcceptTarget{}}, + Rule{Target: AcceptTarget{}}, + Rule{Target: AcceptTarget{}}, + Rule{Target: AcceptTarget{}}, Rule{Target: ErrorTarget{}}, }, BuiltinChains: map[Hook]int{ @@ -135,25 +135,53 @@ func EmptyFilterTable() Table { } } +// A chainVerdict is what a table decides should be done with a packet. +type chainVerdict int + +const ( + // chainAccept indicates the packet should continue through netstack. + chainAccept chainVerdict = iota + + // chainAccept indicates the packet should be dropped. + chainDrop + + // chainReturn indicates the packet should return to the calling chain + // or the underflow rule of a builtin chain. + chainReturn +) + // 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. +// +// Precondition: pkt.NetworkHeader is set. 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. - // Go through each table containing the hook. for _, tablename := range it.Priorities[hook] { - switch verdict := it.checkTable(hook, pkt, tablename); verdict { + table := it.Tables[tablename] + ruleIdx := table.BuiltinChains[hook] + switch verdict := it.checkChain(hook, pkt, table, ruleIdx); verdict { // If the table returns Accept, move on to the next table. - case Accept: + case chainAccept: continue // The Drop verdict is final. - case Drop: + case chainDrop: return false - case Stolen, Queue, Repeat, None, Jump, Return, Continue: - panic(fmt.Sprintf("Unimplemented verdict %v.", verdict)) + case chainReturn: + // Any Return from a built-in chain means we have to + // call the underflow. + underflow := table.Rules[table.Underflows[hook]] + switch v, _ := underflow.Target.Action(pkt); v { + case RuleAccept: + continue + case RuleDrop: + return false + case RuleJump, RuleReturn: + panic("Underflows should only return RuleAccept or RuleDrop.") + default: + panic(fmt.Sprintf("Unknown verdict: %d", v)) + } + default: panic(fmt.Sprintf("Unknown verdict %v.", verdict)) } @@ -163,36 +191,60 @@ func (it *IPTables) Check(hook Hook, pkt tcpip.PacketBuffer) bool { return true } -func (it *IPTables) checkTable(hook Hook, pkt tcpip.PacketBuffer, tablename string) Verdict { +// Precondition: pkt.NetworkHeader is set. +func (it *IPTables) checkChain(hook Hook, pkt tcpip.PacketBuffer, table Table, ruleIdx int) chainVerdict { // Start from ruleIdx and walk the list of rules until a rule gives us // a verdict. - table := it.Tables[tablename] - for ruleIdx := table.BuiltinChains[hook]; ruleIdx < len(table.Rules); ruleIdx++ { - switch verdict := it.checkRule(hook, pkt, table, ruleIdx); verdict { - // In 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)) + for ruleIdx < len(table.Rules) { + switch verdict, jumpTo := it.checkRule(hook, pkt, table, ruleIdx); verdict { + case RuleAccept: + return chainAccept + + case RuleDrop: + return chainDrop + + case RuleReturn: + return chainReturn + + case RuleJump: + // "Jumping" to the next rule just means we're + // continuing on down the list. + if jumpTo == ruleIdx+1 { + ruleIdx++ + continue + } + switch verdict := it.checkChain(hook, pkt, table, jumpTo); verdict { + case chainAccept: + return chainAccept + case chainDrop: + return chainDrop + case chainReturn: + ruleIdx++ + continue + default: + panic(fmt.Sprintf("Unknown verdict: %d", verdict)) + } + default: - panic(fmt.Sprintf("Unknown verdict %v.", verdict)) + panic(fmt.Sprintf("Unknown verdict: %d", verdict)) } + } - panic(fmt.Sprintf("Traversed past the entire list of iptables rules in table %q.", tablename)) + // We got through the entire table without a decision. Default to DROP + // for safety. + return chainDrop } // Precondition: pk.NetworkHeader is set. -func (it *IPTables) checkRule(hook Hook, pkt tcpip.PacketBuffer, table Table, ruleIdx int) Verdict { +func (it *IPTables) checkRule(hook Hook, pkt tcpip.PacketBuffer, table Table, ruleIdx int) (RuleVerdict, int) { rule := table.Rules[ruleIdx] // First check whether the packet matches the IP header filter. // TODO(gvisor.dev/issue/170): Support other fields of the filter. if rule.Filter.Protocol != 0 && rule.Filter.Protocol != header.IPv4(pkt.NetworkHeader).TransportProtocol() { - return Continue + // Continue on to the next rule. + return RuleJump, ruleIdx + 1 } // Go through each rule matcher. If they all match, run @@ -200,14 +252,14 @@ func (it *IPTables) checkRule(hook Hook, pkt tcpip.PacketBuffer, table Table, ru for _, matcher := range rule.Matchers { matches, hotdrop := matcher.Match(hook, pkt, "") if hotdrop { - return Drop + return RuleDrop, 0 } if !matches { - return Continue + // Continue on to the next rule. + return RuleJump, ruleIdx + 1 } } // All the matchers matched, so run the target. - verdict, _ := rule.Target.Action(pkt) - return verdict + return rule.Target.Action(pkt) } |