Re: [lwip-users] netconn_prepare_delete called twice when doing lwip_close leading to errno = EBADF

[Bram Peeters]

Hi

 

And a small  related sideremark:

At the end of lwip_close there is a set_errno(0);

 

I don’t know if that was put there to deal with the situation described below, but it does not do the job given the default implementation of set_errno in sockets_priv.h

#ifndef set_errno
#define set_errno(err) do { if (err) { errno = (err); } } while(0)
#endif

Regards

Bram

 

From: lwip-users <lwip-users-bounces+bram.peeters=dekimo.com@nongnu.org> On Behalf Of Bram Peeters
Sent: Monday, March 15, 2021 16:53
To: lwip-users@nongnu.org
Subject: [lwip-users] netconn_prepare_delete called twice when doing lwip_close leading to errno = EBADF

 

Hi,

 

When doing lwip close I get errno being set to EBADF.

 

This happens with the following callstack:

get_socket( “set_errno(EBADF);” )

event_callback() (“sock = get_socket(s);”)

lwip_netconn_do_delconn (“API_EVENT(msg->conn, NETCONN_EVT_RCVPLUS, 0)”)

<...>

 

Upon investigation I think this is because in the lwip_close scenario  netconn_prepare_delete is called twice.

First time is directly from lwip_close-> netconn_prepare_delete

 

Second time is via lwip_close-> free_socket-> free_socket_free_elements-> netconn_delete-> netconn_prepare_delete

 

The second time could be avoided if LWIP_NETCONN_FULLDUPLEX is set in which case there is a test for it, but I see that is flag is in alpha state and if not needed it is a bit strange to enable it just for this ?

 

But maybe I am misunderstanding something ?

 

Regards,

Bram