[systemd-devel] Why contacting a 'random address' is necessary

[Harry G. Coin]

On 4/22/21 11:00 AM, Mantas Mikulėnas wrote:
> ...
> I'm curious about what brought this problem into existence in the
> first place. Why *is* it necessary to contact a random address within
> the network? (If it's to check that the physical interface is working,
> then just the fact that you somehow acquired a lease would be enough. no?)
>
The only non-destructive way I've found to test whether a real or
virtual nic interface computes packet checksums properly is to send a
small packet to a random address temporarily added to the suspect
interface.  If a bad udp checksum is detected, invert
tx-checksum-ip-generic.



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