Detecting MTU misconfigurations and raise alarms would be a big plus.
Some early thoughts:
When sfunnel is attached in INGRESS, there is no way to know the egress interface at that point in time.
Likewise, route MTU checking happens after sfunnel has been executed when attached on INGRESS and before sfunnel is executed when attached on EGRESS. There is literally no way to know that.
Sidenote: If IPv4 DF=1 is set, Interface counters dropped and/or tx_dropped should increase
What might be more realistic is to define an env variable $DETECT_MAX_MTU=value, and that sfunnel can emit bpf_printk() warnings,with a clear pattern, when funneling exceeds $DETECT_MAX_MTU.
Detecting MTU misconfigurations and raise alarms would be a big plus.
Some early thoughts:
sfunnelis attached in INGRESS, there is no way to know the egress interface at that point in time.sfunnelhas been executed when attached on INGRESS and beforesfunnelis executed when attached on EGRESS. There is literally no way to know that.DF=1is set, Interface countersdroppedand/ortx_droppedshould increaseWhat might be more realistic is to define an env variable
$DETECT_MAX_MTU=value, and thatsfunnelcan emitbpf_printk()warnings,with a clear pattern, when funneling exceeds$DETECT_MAX_MTU.