On 06/27/2018 11:59 AM, Cong Wang wrote:
>
> IIRC, this skb_orphan() was introduced much earlier than TSQ, probably
> from the beginning of veth.
Sigh
SO_SNDBUF was invented years ago before veth.
You focus on TSQ while it is only one of the many things that are broken.
>
> Leaving the stack should be effectively equivalent to leaving the host,
> from the view of network isolation.
>
Having a UDP socket being able to burn a cpu and fill a qdisc is a major bug.
Bu default (blocking send() syscalls) the following loop should
block the thread if socket sk_wmem_alloc hits sk_sndbuf, this is
the beauty of backpressure.
while (1)
send(fd, ...);
With skb_orphan(), sk_wmem_alloc will stay around 0, so the loop will burn a cpu
and fill a qdisc, eventually breaking "network isolation", since other sockets
might be unable to send a single packet.
If you have a concrete case where the skb_orphan() is needed, then you will have
to add a parameter to let the admin opt-in for this.
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