Re: [lwip-users] http server and pbuf overflow

[Bernhard 'Gustl' Bauer]

Hi,

I checked the memory where pbuf pool is located. On power up it is zero 
except for the ->next pointers. Some time later MEM PBUF_POOL used is at 
3 (max=5) in spite there is no traffic. So I checked the memory again. 
The top 3 pbufs (63, 62, 61) are like this:
->next=0
->tot_len=0
->len=0
->ref=1

pbuf (60) is like this:
->next=&pbuf[58]
->tot_len=0
->len=0
->ref=0

pbuf (59) is like this:
->next=&pbuf[59]
->tot_len=0
->len=0
->ref=0

All pbufs with ref=1 are not freed, all pbufs with ref=0 are freed. Is 
this correct?

I crosschecked the pbufs with the attached wireshark file.
pbuf[63] = packet 55
pbuf[62] = packet 128
pbuf[61] = packet 99

In all 3 cases this is a FIN packet from remote after a corrupt 
transfer. From the pcap file I can only guess whether ACK (42, 107, 83) 
and POST (43, 108, 84) are missed, or passed on to my application.

I checked my http_recv(). I have 3 different exits:
1: pbuf_free(); tcp_abort(); return ERR_ABORT;
2: tcp_receved(); pbuf_free(); tcp_abort(); return ERR_ABORT;
3: tcp_receved(); pbuf_free(); return ERR_OK;
Is there anything wrong with an exit? Do I need tcp_recved() before 
tcp_abort(); return ERR_ABORT; ?

Glad for any pointers.

Gustl

debug_20_01_a.pcap
Description: Binary data

debug_20_01_c.pcap
Description: Binary data