diff options
Diffstat (limited to 'pkg/tcpip/stack/iptables.go')
| -rw-r--r-- | pkg/tcpip/stack/iptables.go | 308 |
1 files changed, 175 insertions, 133 deletions
diff --git a/pkg/tcpip/stack/iptables.go b/pkg/tcpip/stack/iptables.go index 443423b3c..110ba073d 100644 --- a/pkg/tcpip/stack/iptables.go +++ b/pkg/tcpip/stack/iptables.go @@ -16,40 +16,49 @@ package stack import ( "fmt" - "strings" + "time" "gvisor.dev/gvisor/pkg/tcpip" "gvisor.dev/gvisor/pkg/tcpip/header" ) -// Table names. +// tableID is an index into IPTables.tables. +type tableID int + const ( - TablenameNat = "nat" - TablenameMangle = "mangle" - TablenameFilter = "filter" + natID tableID = iota + mangleID + filterID + numTables ) -// Chain names as defined by net/ipv4/netfilter/ip_tables.c. +// Table names. const ( - ChainNamePrerouting = "PREROUTING" - ChainNameInput = "INPUT" - ChainNameForward = "FORWARD" - ChainNameOutput = "OUTPUT" - ChainNamePostrouting = "POSTROUTING" + NATTable = "nat" + MangleTable = "mangle" + FilterTable = "filter" ) +// nameToID is immutable. +var nameToID = map[string]tableID{ + NATTable: natID, + MangleTable: mangleID, + FilterTable: filterID, +} + // HookUnset indicates that there is no hook set for an entrypoint or // underflow. const HookUnset = -1 +// reaperDelay is how long to wait before starting to reap connections. +const reaperDelay = 5 * time.Second + // DefaultTables returns a default set of tables. Each chain is set to accept // all packets. -func DefaultTables() IPTables { - // TODO(gvisor.dev/issue/170): We may be able to swap out some strings for - // iotas. - return IPTables{ - Tables: map[string]Table{ - TablenameNat: Table{ +func DefaultTables() *IPTables { + return &IPTables{ + tables: [numTables]Table{ + natID: Table{ Rules: []Rule{ Rule{Target: AcceptTarget{}}, Rule{Target: AcceptTarget{}}, @@ -57,65 +66,71 @@ func DefaultTables() IPTables { Rule{Target: AcceptTarget{}}, Rule{Target: ErrorTarget{}}, }, - BuiltinChains: map[Hook]int{ + BuiltinChains: [NumHooks]int{ Prerouting: 0, Input: 1, + Forward: HookUnset, Output: 2, Postrouting: 3, }, - Underflows: map[Hook]int{ + Underflows: [NumHooks]int{ Prerouting: 0, Input: 1, + Forward: HookUnset, Output: 2, Postrouting: 3, }, - UserChains: map[string]int{}, }, - TablenameMangle: Table{ + mangleID: Table{ Rules: []Rule{ Rule{Target: AcceptTarget{}}, Rule{Target: AcceptTarget{}}, Rule{Target: ErrorTarget{}}, }, - BuiltinChains: map[Hook]int{ + BuiltinChains: [NumHooks]int{ Prerouting: 0, Output: 1, }, - Underflows: map[Hook]int{ - Prerouting: 0, - Output: 1, + Underflows: [NumHooks]int{ + Prerouting: 0, + Input: HookUnset, + Forward: HookUnset, + Output: 1, + Postrouting: HookUnset, }, - UserChains: map[string]int{}, }, - TablenameFilter: Table{ + filterID: Table{ Rules: []Rule{ Rule{Target: AcceptTarget{}}, Rule{Target: AcceptTarget{}}, Rule{Target: AcceptTarget{}}, Rule{Target: ErrorTarget{}}, }, - BuiltinChains: map[Hook]int{ - Input: 0, - Forward: 1, - Output: 2, + BuiltinChains: [NumHooks]int{ + Prerouting: HookUnset, + Input: 0, + Forward: 1, + Output: 2, + Postrouting: HookUnset, }, - Underflows: map[Hook]int{ - Input: 0, - Forward: 1, - Output: 2, + Underflows: [NumHooks]int{ + Prerouting: HookUnset, + Input: 0, + Forward: 1, + Output: 2, + Postrouting: HookUnset, }, - UserChains: map[string]int{}, }, }, - Priorities: map[Hook][]string{ - Input: []string{TablenameNat, TablenameFilter}, - Prerouting: []string{TablenameMangle, TablenameNat}, - Output: []string{TablenameMangle, TablenameNat, TablenameFilter}, + priorities: [NumHooks][]tableID{ + Prerouting: []tableID{mangleID, natID}, + Input: []tableID{natID, filterID}, + Output: []tableID{mangleID, natID, filterID}, }, - connections: ConnTrackTable{ - CtMap: make(map[uint32]ConnTrackTupleHolder), - Seed: generateRandUint32(), + connections: ConnTrack{ + seed: generateRandUint32(), }, + reaperDone: make(chan struct{}, 1), } } @@ -124,41 +139,61 @@ func DefaultTables() IPTables { func EmptyFilterTable() Table { return Table{ Rules: []Rule{}, - BuiltinChains: map[Hook]int{ - Input: HookUnset, - Forward: HookUnset, - Output: HookUnset, + BuiltinChains: [NumHooks]int{ + Prerouting: HookUnset, + Postrouting: HookUnset, }, - Underflows: map[Hook]int{ - Input: HookUnset, - Forward: HookUnset, - Output: HookUnset, + Underflows: [NumHooks]int{ + Prerouting: HookUnset, + Postrouting: HookUnset, }, - UserChains: map[string]int{}, } } -// EmptyNatTable returns a Table with no rules and the filter table chains +// EmptyNATTable returns a Table with no rules and the filter table chains // mapped to HookUnset. -func EmptyNatTable() Table { +func EmptyNATTable() Table { return Table{ Rules: []Rule{}, - BuiltinChains: map[Hook]int{ - Prerouting: HookUnset, - Input: HookUnset, - Output: HookUnset, - Postrouting: HookUnset, + BuiltinChains: [NumHooks]int{ + Forward: HookUnset, }, - Underflows: map[Hook]int{ - Prerouting: HookUnset, - Input: HookUnset, - Output: HookUnset, - Postrouting: HookUnset, + Underflows: [NumHooks]int{ + Forward: HookUnset, }, - UserChains: map[string]int{}, } } +// GetTable returns a table by name. +func (it *IPTables) GetTable(name string) (Table, bool) { + id, ok := nameToID[name] + if !ok { + return Table{}, false + } + it.mu.RLock() + defer it.mu.RUnlock() + return it.tables[id], true +} + +// ReplaceTable replaces or inserts table by name. +func (it *IPTables) ReplaceTable(name string, table Table) *tcpip.Error { + id, ok := nameToID[name] + if !ok { + return tcpip.ErrInvalidOptionValue + } + it.mu.Lock() + defer it.mu.Unlock() + // If iptables is being enabled, initialize the conntrack table and + // reaper. + if !it.modified { + it.connections.buckets = make([]bucket, numBuckets) + it.startReaper(reaperDelay) + } + it.modified = true + it.tables[id] = table + return nil +} + // A chainVerdict is what a table decides should be done with a packet. type chainVerdict int @@ -180,13 +215,27 @@ const ( // // Precondition: pkt.NetworkHeader is set. func (it *IPTables) Check(hook Hook, pkt *PacketBuffer, gso *GSO, r *Route, address tcpip.Address, nicName string) bool { + // Many users never configure iptables. Spare them the cost of rule + // traversal if rules have never been set. + it.mu.RLock() + defer it.mu.RUnlock() + if !it.modified { + return true + } + // Packets are manipulated only if connection and matching // NAT rule exists. - it.connections.HandlePacket(pkt, hook, gso, r) + shouldTrack := it.connections.handlePacket(pkt, hook, gso, r) // Go through each table containing the hook. - for _, tablename := range it.Priorities[hook] { - table := it.Tables[tablename] + priorities := it.priorities[hook] + for _, tableID := range priorities { + // If handlePacket already NATed the packet, we don't need to + // check the NAT table. + if tableID == natID && pkt.NatDone { + continue + } + table := it.tables[tableID] ruleIdx := table.BuiltinChains[hook] switch verdict := it.checkChain(hook, pkt, table, ruleIdx, gso, r, address, nicName); verdict { // If the table returns Accept, move on to the next table. @@ -215,17 +264,59 @@ func (it *IPTables) Check(hook Hook, pkt *PacketBuffer, gso *GSO, r *Route, addr } } + // If this connection should be tracked, try to add an entry for it. If + // traversing the nat table didn't end in adding an entry, + // maybeInsertNoop will add a no-op entry for the connection. This is + // needeed when establishing connections so that the SYN/ACK reply to an + // outgoing SYN is delivered to the correct endpoint rather than being + // redirected by a prerouting rule. + // + // From the iptables documentation: "If there is no rule, a `null' + // binding is created: this usually does not map the packet, but exists + // to ensure we don't map another stream over an existing one." + if shouldTrack { + it.connections.maybeInsertNoop(pkt, hook) + } + // Every table returned Accept. return true } +// beforeSave is invoked by stateify. +func (it *IPTables) beforeSave() { + // Ensure the reaper exits cleanly. + it.reaperDone <- struct{}{} + // Prevent others from modifying the connection table. + it.connections.mu.Lock() +} + +// afterLoad is invoked by stateify. +func (it *IPTables) afterLoad() { + it.startReaper(reaperDelay) +} + +// startReaper starts a goroutine that wakes up periodically to reap timed out +// connections. +func (it *IPTables) startReaper(interval time.Duration) { + go func() { // S/R-SAFE: reaperDone is signalled when iptables is saved. + bucket := 0 + for { + select { + case <-it.reaperDone: + return + case <-time.After(interval): + bucket, interval = it.connections.reapUnused(bucket, interval) + } + } + }() +} + // CheckPackets runs pkts through the rules for hook and returns a map of packets that // should not go forward. // -// Precondition: pkt is a IPv4 packet of at least length header.IPv4MinimumSize. -// -// TODO(gvisor.dev/issue/170): pk.NetworkHeader will always be set as a -// precondition. +// Preconditions: +// - pkt is a IPv4 packet of at least length header.IPv4MinimumSize. +// - pkt.NetworkHeader is not nil. // // NOTE: unlike the Check API the returned map contains packets that should be // dropped. @@ -249,9 +340,9 @@ func (it *IPTables) CheckPackets(hook Hook, pkts PacketBufferList, gso *GSO, r * return drop, natPkts } -// Precondition: pkt is a IPv4 packet of at least length header.IPv4MinimumSize. -// TODO(gvisor.dev/issue/170): pkt.NetworkHeader will always be set as a -// precondition. +// Preconditions: +// - pkt is a IPv4 packet of at least length header.IPv4MinimumSize. +// - pkt.NetworkHeader is not nil. func (it *IPTables) checkChain(hook Hook, pkt *PacketBuffer, table Table, ruleIdx int, gso *GSO, r *Route, address tcpip.Address, nicName string) chainVerdict { // Start from ruleIdx and walk the list of rules until a rule gives us // a verdict. @@ -296,25 +387,14 @@ func (it *IPTables) checkChain(hook Hook, pkt *PacketBuffer, table Table, ruleId return chainDrop } -// Precondition: pkt is a IPv4 packet of at least length header.IPv4MinimumSize. -// TODO(gvisor.dev/issue/170): pkt.NetworkHeader will always be set as a -// precondition. +// Preconditions: +// - pkt is a IPv4 packet of at least length header.IPv4MinimumSize. +// - pkt.NetworkHeader is not nil. func (it *IPTables) checkRule(hook Hook, pkt *PacketBuffer, table Table, ruleIdx int, gso *GSO, r *Route, address tcpip.Address, nicName string) (RuleVerdict, int) { rule := table.Rules[ruleIdx] - // If pkt.NetworkHeader hasn't been set yet, it will be contained in - // pkt.Data. - if pkt.NetworkHeader == nil { - var ok bool - pkt.NetworkHeader, ok = pkt.Data.PullUp(header.IPv4MinimumSize) - if !ok { - // Precondition has been violated. - panic(fmt.Sprintf("iptables checks require IPv4 headers of at least %d bytes", header.IPv4MinimumSize)) - } - } - // Check whether the packet matches the IP header filter. - if !filterMatch(rule.Filter, header.IPv4(pkt.NetworkHeader), hook, nicName) { + if !rule.Filter.match(header.IPv4(pkt.NetworkHeader), hook, nicName) { // Continue on to the next rule. return RuleJump, ruleIdx + 1 } @@ -322,7 +402,7 @@ func (it *IPTables) checkRule(hook Hook, pkt *PacketBuffer, table Table, 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, "") + matches, hotdrop := matcher.Match(hook, pkt, "") if hotdrop { return RuleDrop, 0 } @@ -336,46 +416,8 @@ func (it *IPTables) checkRule(hook Hook, pkt *PacketBuffer, table Table, ruleIdx return rule.Target.Action(pkt, &it.connections, hook, gso, r, address) } -func filterMatch(filter IPHeaderFilter, hdr header.IPv4, hook Hook, nicName string) bool { - // TODO(gvisor.dev/issue/170): Support other fields of the filter. - // Check the transport protocol. - if filter.Protocol != 0 && filter.Protocol != hdr.TransportProtocol() { - return false - } - - // Check the destination IP. - dest := hdr.DestinationAddress() - matches := true - for i := range filter.Dst { - if dest[i]&filter.DstMask[i] != filter.Dst[i] { - matches = false - break - } - } - if matches == filter.DstInvert { - return false - } - - // Check the output interface. - // TODO(gvisor.dev/issue/170): Add the check for FORWARD and POSTROUTING - // hooks after supported. - if hook == Output { - n := len(filter.OutputInterface) - if n == 0 { - return true - } - - // If the interface name ends with '+', any interface which begins - // with the name should be matched. - ifName := filter.OutputInterface - matches = true - if strings.HasSuffix(ifName, "+") { - matches = strings.HasPrefix(nicName, ifName[:n-1]) - } else { - matches = nicName == ifName - } - return filter.OutputInterfaceInvert != matches - } - - return true +// OriginalDst returns the original destination of redirected connections. It +// returns an error if the connection doesn't exist or isn't redirected. +func (it *IPTables) OriginalDst(epID TransportEndpointID) (tcpip.Address, uint16, *tcpip.Error) { + return it.connections.originalDst(epID) } |