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[client] Make mss clamping optional for nftables #4843

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Merged
lixmal merged 3 commits into from
Nov 22, 2025
Merged

[client] Make mss clamping optional for nftables #4843

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677e75f
Make mss clamping optional for nftables
lixmal Nov 22, 2025
3900128
Make listing tables infallible
lixmal Nov 22, 2025
594ee37
Remove redundant return
lixmal Nov 22, 2025
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35 changes: 13 additions & 22 deletions client/firewall/nftables/router_linux.go
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Original file line number Diff line number Diff line change
Expand Up @@ -91,11 +91,7 @@ func newRouter(workTable *nftables.Table, wgIface iFaceMapper, mtu uint16) (*rou
var err error
r.filterTable, err = r.loadFilterTable()
if err != nil {
if errors.Is(err, errFilterTableNotFound) {
log.Warnf("table 'filter' not found for forward rules")
} else {
return nil, fmt.Errorf("load filter table: %w", err)
}
log.Warnf("failed to load filter table, skipping accept rules: %v", err)
}

return r, nil
Expand Down Expand Up @@ -175,7 +171,7 @@ func (r *router) removeNatPreroutingRules() error {
func (r *router) loadFilterTable() (*nftables.Table, error) {
tables, err := r.conn.ListTablesOfFamily(nftables.TableFamilyIPv4)
if err != nil {
return nil, fmt.Errorf("unable to list tables: %v", err)
return nil, fmt.Errorf("list tables: %w", err)
}

for _, table := range tables {
Expand All @@ -193,8 +189,6 @@ func (r *router) createContainers() error {
Table: r.workTable,
})

insertReturnTrafficRule(r.conn, r.workTable, r.chains[chainNameRoutingFw])

prio := *nftables.ChainPriorityNATSource - 1
r.chains[chainNameRoutingNat] = r.conn.AddChain(&nftables.Chain{
Name: chainNameRoutingNat,
Expand Down Expand Up @@ -236,9 +230,12 @@ func (r *router) createContainers() error {
Type: nftables.ChainTypeFilter,
})

// Add the single NAT rule that matches on mark
if err := r.addPostroutingRules(); err != nil {
return fmt.Errorf("add single nat rule: %v", err)
insertReturnTrafficRule(r.conn, r.workTable, r.chains[chainNameRoutingFw])

r.addPostroutingRules()

if err := r.conn.Flush(); err != nil {
return fmt.Errorf("initialize tables: %v", err)
}

if err := r.addMSSClampingRules(); err != nil {
Expand All @@ -250,11 +247,7 @@ func (r *router) createContainers() error {
}

if err := r.refreshRulesMap(); err != nil {
log.Errorf("failed to clean up rules from FORWARD chain: %s", err)
}

if err := r.conn.Flush(); err != nil {
return fmt.Errorf("initialize tables: %v", err)
log.Errorf("failed to refresh rules: %s", err)
}

return nil
Expand Down Expand Up @@ -695,7 +688,7 @@ func (r *router) addNatRule(pair firewall.RouterPair) error {
}

// addPostroutingRules adds the masquerade rules
func (r *router) addPostroutingRules() error {
func (r *router) addPostroutingRules() {
// First masquerade rule for traffic coming in from WireGuard interface
exprs := []expr.Any{
// Match on the first fwmark
Expand Down Expand Up @@ -761,8 +754,6 @@ func (r *router) addPostroutingRules() error {
Chain: r.chains[chainNameRoutingNat],
Exprs: exprs2,
})

return nil
}

// addMSSClampingRules adds MSS clamping rules to prevent fragmentation for forwarded traffic.
Expand Down Expand Up @@ -839,7 +830,7 @@ func (r *router) addMSSClampingRules() error {
Exprs: exprsOut,
})

return nil
return r.conn.Flush()
}

// addLegacyRouteRule adds a legacy routing rule for mgmt servers pre route acls
Expand Down Expand Up @@ -1068,7 +1059,7 @@ func (r *router) acceptFilterRulesNftables() error {
}
r.conn.InsertRule(inputRule)

return nil
return r.conn.Flush()
}

func (r *router) removeAcceptFilterRules() error {
Expand Down Expand Up @@ -1196,7 +1187,7 @@ func (r *router) refreshRulesMap() error {
for _, chain := range r.chains {
rules, err := r.conn.GetRules(chain.Table, chain)
if err != nil {
return fmt.Errorf(" unable to list rules: %v", err)
return fmt.Errorf("list rules: %w", err)
}
for _, rule := range rules {
if len(rule.UserData) > 0 {
Expand Down
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