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metal-stack / firewall-controller

A kubernetes controller running on bare-metal firewalls, creating nftables rules, configures suricata, collects network metrics
MIT License
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source port reuse in egress masquerading #180

Closed mwennrich closed 5 months ago

mwennrich commented 6 months ago

currently source ports do not get changed during source-NAT:

15:18:50.762235 vlan776 In  IP 10.67.144.1.44819 > 141.1.1.1.80: Flags [S], seq 2793823730, win 35840, options [mss 8960,sackOK,TS val 366183215 ecr 0,nop,wscale 14], length 0
15:18:50.762308 vlan104009 Out IP 212.34.85.43.44819 > 141.1.1.1.80: Flags [S], seq 2793823730, win 35840, options [mss 8960,sackOK,TS val 366183215 ecr 0,nop,wscale 14], length 0

and calico is configured by gardener-extension-provider-calico to only use half of the possible source ports for NAT:

            - name: FELIX_NATPORTRANGE
              value: "32768:65535"

On clusters with a lot of nodes and with a lot of connections to the same backend, this can lead to too early reuse of source ports, which then get dropped by the target or by a firewall in between.