Re: [lwip-users] bind with link down

[Simon Goldschmidt]

On 31.03.2020 21:34, Massimiliano Cialdi wrote:
> I have a process that polls the PHY to find out if the link is up or
> down. It calls netif_set_link_up()/netif_set_link_down(). I also have
> the link callback calling netif_set_up()/netif_set_down().

You're mixing link state with admin state here. That might work, but
might not work in some situations.

> I wonder what happens if the functions:
>    conn = netconn_new(NETCONN_UDP);
>    netconn_bind(conn, IP_ADDR_ANY, 7);
> are called when netif is still down. This happens because, for
> example, the udpecho_thread() process starts before the netif is up.
>
> Then when the link goes down while
>     err = netconn_recv(conn, &buf);
> is waiting, it doesn't exit with an error. Is that correct?

Correct or not depends on how you define it. There's currently no code
in lwIP to unblock on link loss. That could only work if you're bound to
a netif. I'm not sure if what you think of works in other stacks.

Regards,
Simon