diff options
Diffstat (limited to 'pkg/tcpip/stack/iptables.go')
| -rw-r--r-- | pkg/tcpip/stack/iptables.go | 245 |
1 files changed, 149 insertions, 96 deletions
diff --git a/pkg/tcpip/stack/iptables.go b/pkg/tcpip/stack/iptables.go index 974d77c36..cbbae4224 100644 --- a/pkg/tcpip/stack/iptables.go +++ b/pkg/tcpip/stack/iptables.go @@ -16,39 +16,49 @@ package stack import ( "fmt" + "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{ + tables: [numTables]Table{ + natID: Table{ Rules: []Rule{ Rule{Target: AcceptTarget{}}, Rule{Target: AcceptTarget{}}, @@ -56,64 +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: ConnTrack{ - conns: make(map[tupleID]tuple), + seed: generateRandUint32(), }, + reaperDone: make(chan struct{}, 1), } } @@ -122,62 +139,59 @@ 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 table by name. +// 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() - t, ok := it.tables[name] - return t, ok + return it.tables[id], true } // ReplaceTable replaces or inserts table by name. -func (it *IPTables) ReplaceTable(name string, table Table) { +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[name] = table -} - -// GetPriorities returns slice of priorities associated with hook. -func (it *IPTables) GetPriorities(hook Hook) []string { - it.mu.RLock() - defer it.mu.RUnlock() - return it.priorities[hook] + it.tables[id] = table + return nil } // A chainVerdict is what a table decides should be done with a packet. @@ -212,11 +226,19 @@ func (it *IPTables) Check(hook Hook, pkt *PacketBuffer, gso *GSO, r *Route, addr // 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.GetPriorities(hook) { - table, _ := it.GetTable(tablename) + it.mu.RLock() + defer it.mu.RUnlock() + 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. @@ -245,17 +267,59 @@ 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. @@ -279,9 +343,9 @@ 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. @@ -326,23 +390,12 @@ 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 !rule.Filter.match(header.IPv4(pkt.NetworkHeader), hook, nicName) { // Continue on to the next rule. |