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Re: [lwip-users] Multicast and ICMP-Echo
From: |
Sylvain Rochet |
Subject: |
Re: [lwip-users] Multicast and ICMP-Echo |
Date: |
Wed, 13 May 2015 10:23:16 +0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
Hello Thomas,
On Wed, May 06, 2015 at 02:23:50PM -0300, Thomas Ubensee wrote:
> I was trying to ping a multicast address on a LWIP-Stack (using the master
> code) with LWIP_MULTICAST_PING enabled.
> I could see in Wireshark that lwip send an ICMP-echo which linux ping did
> not recognize. It seems to me that the problem is that LWIP responses the
> ICMP-echo with the multicast-address as source and NOT with the unicast
> address of the interface where the ICMP-Request came from.
> When changing the code inside of icmp.c around line 190 from:
>
> ...
> /* At this point, all checks are OK. */
> /* We generate an answer by switching the dest and src ip addresses,
> * setting the icmp type to ECHO_RESPONSE and updating the checksum. */
> iecho = (struct icmp_echo_hdr *)p->payload;
>
> ip_addr_copy(iphdr->src, *ip_current_dest_addr());
> ip_addr_copy(iphdr->dest, *ip_current_src_addr());
> ICMPH_TYPE_SET(iecho, ICMP_ER);
> #if CHECKSUM_GEN_ICMP
> ...
>
>
> to:
> ...
> /* At this point, all checks are OK. */
> /* We generate an answer by switching the dest and src ip addresses,
> * setting the icmp type to ECHO_RESPONSE and updating the checksum. */
> iecho = (struct icmp_echo_hdr *)p->payload;
>
> #if LWIP_MULTICAST_PING
>
> if (ip_addr_ismulticast(ip_current_dest_addr())) {
> /*Replace Multicast address with interface ip address*/
> ip_addr_copy(iphdr->src, inp->ip_addr);
> }
> else {
> ip_addr_copy(iphdr->src, *ip_current_dest_addr());
> }
> #else
> ip_addr_copy(iphdr->src, *ip_current_dest_addr());
> #endif
> ip_addr_copy(iphdr->dest, *ip_current_src_addr());
> ICMPH_TYPE_SET(iecho, ICMP_ER);
> #if CHECKSUM_GEN_ICMP
> ...
>
> Linux ping works fine.
Could you post your patch on the lwIP patch tracker so it doesn't get
forgotten ? :)
Using git format-patch format and against master head if possible.
Sylvain
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