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AW: [lwip-devel] R: [lwip-users] Sending to myself
From: |
Goldschmidt Simon |
Subject: |
AW: [lwip-devel] R: [lwip-users] Sending to myself |
Date: |
Thu, 10 Jan 2008 12:38:09 +0100 |
Copying the code to your netif would also work.
The important thing here is that you MUST NEVER call ip_input from your
netif_output function (the TCP part of the lwip core is not reentrant since it
uses some global variables)!
Therefore, the loopif has changed in the CVS version:
- without an OS (raw API only, no netconn or sockets api), it uses a queue for
the ouput packets and empties that queue when loopif_poll is called (must be
from the main loop, not from inside a core stack function)
- with an OS (using tcpip_thread/tcpip.c ...), it can call netif->input
directly since this leads to putting the packet on a queue inside tcpip_thread.
So when implementing it yourself, you have to choose the right way to do it
depending on your setup (OS or no OS).
Simon
-----Ursprüngliche Nachricht-----
Von: address@hidden [mailto:address@hidden Im Auftrag von Ceresoli Luca
Gesendet: Donnerstag, 10. Januar 2008 12:24
An: address@hidden
Betreff: [lwip-devel] R: [lwip-users] Sending to myself
Hi Simon,
thanks for the advice. I tried to implement what you suggested, but it still
has some issues.
The changes to the lwip code are in the attached patch.
Changes to user code are limited to adding a loopif and calling loopif_poll().
I can now send UDP packets to myself, but:
- If the sender pcb is not bound to the local address, I receive
the packets with a sender IP equal to 127.0.0.1.
- If the sender pcb is bound to my local address, the packets are
dropped by udp_sendto_if() where it checks pcb->local_ip.
I fear hacking further in this direction would be pretty invasive.
I think I'll try another approach: copying the queue management stuff into
netif, so it works within the netif itself. Do you foresee anything that makes
this a bad idea?
Luca Ceresoli
-----Messaggio originale-----
Da: address@hidden
[mailto:address@hidden conto di Goldschmidt Simon
Inviato: mercoledì 9 gennaio 2008 17.19
A: Mailing list for lwIP users
Oggetto: RE: [lwip-users] Sending to myself
Hi,
The routine you created is already included in loopif.c (the loopback
interface). You only would have to make sure that packets sent to your own
external IP get sent over the loopback interface. The method to implement that
would be ip_route().
Simon
-----Ursprüngliche Nachricht-----
Von: address@hidden [mailto:address@hidden Im Auftrag von Ceresoli Luca
Gesendet: Mittwoch, 9. Januar 2008 16:23
An: address@hidden
Betreff: [lwip-users] Sending to myself
Hi,
I'm not sure if this is a bug or a missing feature, but here it is: lwip does
not send packets to its own IP address.
I use raw API, NO_SYS=1, lwip CVS dec 11, 2007.
I see that the code simply does not check if dest_IP == own_IP.
This leads to gratuitous ARP requests, which cannot be answered.
I think the most logical solution would be to redirect the packet up the stack
when it has reached down to the IP level. But in the absence of any packet
queue, this would increase the used (processor) stack depth and potentially
introduce loops.
Currently I solved it implementing the following netif->output(), which seems
to work, but with heavy (processor) stack load.
err_t myif_output(struct netif* netif, struct pbuf* p, struct ip_addr* dest_ip)
{
if (ip_addr_cmp(dest_ip, &netif->ip_addr))
return netif->input(p, netif);
else
return etharp_output(netif, p, dest_ip); }
- Is the above routine safe?
- Is there any safe and clean way to add this feature, possibly to lwip itself,
avoiding deep (processor) stack usage?
Thanks in advance,
Luca Ceresoli
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