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util/linuxfw: fix IPv6 availability check for nftables (#12009)

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* util/linuxfw: fix IPv6 NAT availability check for nftables

When running firewall in nftables mode,
there is no need for a separate NAT availability check
(unlike with iptables, there are no hosts that support nftables, but not IPv6 NAT - see tailscale/tailscale#11353).
This change fixes a firewall NAT availability check that was using the no-longer set ipv6NATAvailable field
by removing the field and using a method that, for nftables, just checks that IPv6 is available.

Updates tailscale/tailscale#12008

Signed-off-by: Irbe Krumina <irbe@tailscale.com>
This commit is contained in:
Irbe Krumina
2024-05-14 08:51:53 +01:00
committed by GitHub
parent 8aa5c3534d
commit 7ef2f72135
4 changed files with 106 additions and 77 deletions
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49
util/linuxfw/nftables_runner.go
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@ -41,8 +41,9 @@ type chainInfo struct {
chainPolicy *nftables.ChainPolicy
}
// nftable contains nat and filter tables for the given IP family (Proto).
type nftable struct {
Proto nftables.TableFamily
Proto nftables.TableFamily // IPv4 or IPv6
Filter *nftables.Table
Nat *nftables.Table
}
@ -69,11 +70,10 @@ type nftable struct {
// https://wiki.nftables.org/wiki-nftables/index.php/Configuring_chains
type nftablesRunner struct {
conn *nftables.Conn
nft4 *nftable
nft6 *nftable
nft4 *nftable // IPv4 tables
nft6 *nftable // IPv6 tables
v6Available bool
v6NATAvailable bool
v6Available bool // whether the host supports IPv6
}
func (n *nftablesRunner) ensurePreroutingChain(dst netip.Addr) (*nftables.Table, *nftables.Chain, error) {
@ -598,6 +598,10 @@ func newNfTablesRunner(logf logger.Logf) (*nftablesRunner, error) {
if err != nil {
return nil, fmt.Errorf("nftables connection: %w", err)
}
return newNfTablesRunnerWithConn(logf, conn), nil
}
func newNfTablesRunnerWithConn(logf logger.Logf, conn *nftables.Conn) *nftablesRunner {
nft4 := &nftable{Proto: nftables.TableFamilyIPv4}
v6err := CheckIPv6(logf)
@ -609,8 +613,8 @@ func newNfTablesRunner(logf logger.Logf) (*nftablesRunner, error) {
if supportsV6 {
nft6 = &nftable{Proto: nftables.TableFamilyIPv6}
logf("v6nat availability: true")
}
logf("netfilter running in nftables mode, v6 = %v", supportsV6)
// TODO(KevinLiang10): convert iptables rule to nftable rules if they exist in the iptables
@ -619,7 +623,7 @@ func newNfTablesRunner(logf logger.Logf) (*nftablesRunner, error) {
nft4: nft4,
nft6: nft6,
v6Available: supportsV6,
}, nil
}
}
// newLoadSaddrExpr creates a new nftables expression that loads the source
@ -837,24 +841,15 @@ func (n *nftablesRunner) DelLoopbackRule(addr netip.Addr) error {
return n.conn.Flush()
}
// getTables gets the available nftable in nftables runner.
// getTables returns tables for IP families that this host was determined to
// support (either IPv4 and IPv6 or just IPv4).
func (n *nftablesRunner) getTables() []*nftable {
if n.v6Available {
if n.HasIPV6() {
return []*nftable{n.nft4, n.nft6}
}
return []*nftable{n.nft4}
}
// getNATTables gets the available nftable in nftables runner.
// If the system does not support IPv6 NAT, only the IPv4 nftable
// will be returned.
func (n *nftablesRunner) getNATTables() []*nftable {
if n.v6NATAvailable {
return n.getTables()
}
return []*nftable{n.nft4}
}
// AddChains creates custom Tailscale chains in netfilter via nftables
// if the ts-chain doesn't already exist.
func (n *nftablesRunner) AddChains() error {
@ -883,9 +878,7 @@ func (n *nftablesRunner) AddChains() error {
if err = createChainIfNotExist(n.conn, chainInfo{filter, chainNameInput, chainTypeRegular, nil, nil, nil}); err != nil {
return fmt.Errorf("create input chain: %w", err)
}
}
for _, table := range n.getNATTables() {
// Create the nat table if it doesn't exist, this table name is the same
// as the name used by iptables-nft and ufw. We install rules into the
// same conventional table so that `accept` verdicts from our jump
@ -923,7 +916,7 @@ const (
// can be used. It cleans up the dummy chains after creation.
func (n *nftablesRunner) createDummyPostroutingChains() (retErr error) {
polAccept := ptr.To(nftables.ChainPolicyAccept)
for _, table := range n.getNATTables() {
for _, table := range n.getTables() {
nat, err := createTableIfNotExist(n.conn, table.Proto, tsDummyTableName)
if err != nil {
return fmt.Errorf("create nat table: %w", err)
@ -980,7 +973,7 @@ func (n *nftablesRunner) DelChains() error {
return fmt.Errorf("delete chain: %w", err)
}
if n.v6NATAvailable {
if n.HasIPV6NAT() {
if err := deleteChainIfExists(n.conn, n.nft6.Nat, chainNamePostrouting); err != nil {
return fmt.Errorf("delete chain: %w", err)
}
@ -1046,9 +1039,7 @@ func (n *nftablesRunner) AddHooks() error {
if err != nil {
return fmt.Errorf("Addhook: %w", err)
}
}
for _, table := range n.getNATTables() {
postroutingChain, err := getChainFromTable(conn, table.Nat, "POSTROUTING")
if err != nil {
return fmt.Errorf("get INPUT chain: %w", err)
@ -1102,9 +1093,7 @@ func (n *nftablesRunner) DelHooks(logf logger.Logf) error {
if err != nil {
return fmt.Errorf("delhook: %w", err)
}
}
for _, table := range n.getNATTables() {
postroutingChain, err := getChainFromTable(conn, table.Nat, "POSTROUTING")
if err != nil {
return fmt.Errorf("get INPUT chain: %w", err)
@ -1612,9 +1601,7 @@ func (n *nftablesRunner) DelBase() error {
return fmt.Errorf("get forward chain: %v", err)
}
conn.FlushChain(forwardChain)
}
for _, table := range n.getNATTables() {
postrouteChain, err := getChainFromTable(conn, table.Nat, chainNamePostrouting)
if err != nil {
return fmt.Errorf("get postrouting chain v4: %v", err)
@ -1684,7 +1671,7 @@ func addMatchSubnetRouteMarkRule(conn *nftables.Conn, table *nftables.Table, cha
func (n *nftablesRunner) AddSNATRule() error {
conn := n.conn
for _, table := range n.getNATTables() {
for _, table := range n.getTables() {
chain, err := getChainFromTable(conn, table.Nat, chainNamePostrouting)
if err != nil {
return fmt.Errorf("get postrouting chain v4: %w", err)
@ -1727,7 +1714,7 @@ func (n *nftablesRunner) DelSNATRule() error {
&expr.Masq{},
}
for _, table := range n.getNATTables() {
for _, table := range n.getTables() {
chain, err := getChainFromTable(conn, table.Nat, chainNamePostrouting)
if err != nil {
return fmt.Errorf("get postrouting chain v4: %w", err)