[lwip-users] Minimal application segmentation fault

[e8h3wy]

Hello Everyone,

I am new to LWIP and I am wondering if someone could help me with a problem
that I am facing. I compiled the minimal application in LWIP-1.1.1 on a tun
enabled Linux-2.6.14 kernel. When I run the application, it starts
successfully and I see a new tap interface created. However, when I try to
connect to port 7 of 192.168.0.2 using an echo client, LWIP seg faults. It
faults even if I ping to 192.168.0.2 address. In fact, I see the same
behavior when I ping/echoclient to any other address in the 192.168.0 subnet
other than 192.168.0.1. By inserting some printfs, I find that seg fault
occurs in low_level_output function. First, an ARP_REQUEST packet is
received by mintapif_input, to which etharp_arp_input sends an ARP reply by
calling low_level_output, which causes the seg fault while consolidating the
pbuf chain into a buffer for write. I don't want to go further with the
debugging because, I have a feeling that I am missing something basic. Also,
I had to make the following changes to the code in order to compile the
minimal application. 

1. Remove "#define ETHARP_ALWAYS_INSERT 0" from lwipopts.h file

2. Change the signatures of ip/arp input functions as follows in
lwip-1.1.1/src/netif/etharp.c and lwip-1.1.1/src/include/netif/etharp.h
files:

void etharp_ip_input(struct netif *netif, struct pbuf *p);  ------------> 
struct pbuf *  etharp_ip_input(struct netif *netif, struct pbuf *p);

void etharp_arp_input(struct netif *netif, struct eth_addr *ethaddr, struct
pbuf *p); --------------> struct pbuf *  etharp_arp_input(struct netif
*netif, struct eth_addr *ethaddr, struct pbuf *p);

I would really appreciate if someone could point to me what I could be doing
wrong.

Best Regards,
Dennis
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