Re: [lwip-devel] Problem with LWIP_ERROR in pbuf_header(..)

[Fredrik Hederstierna]

> > That is if incomming UDP packet is too short,
so the call to
> > pbuf_header() will trig LWIP_ERROR? 
> > Isn't it better to just drop illegal-size packets instead of
ASSERT? 
> > What if header and header length is corrupted? 
> 
> In the case you mention, shouldn't the first clause in the if statement
> "if (p->tot_len < (IPH_HL(iphdr) * 4 + UDP_HLEN)"
 protect us from the
> assertion?  I.e. if the packet is short it should do that clause,
but
> then not the pbuf_header() call.
> 
> Also, it's a good idea subscribe to lwip-devel to make sure you see
> replies to your questions.  I've CC'd you as I noticed in this
case that
> you're not subscribed, but I don't always realise!

About configure lwIP correct:

How can we protect us from incoming packets with malformed
headers or too large headers?

We config lwIP like this


#define
LWIP_RAW 0
#define
LWIP_DHCP 1

#define
IP_REASSEMBLY 0

#define
ARP_QUEUEING 1

#define
ARP_TABLE_SIZE 4

#define
PBUF_POOL_SIZE 10

#define
MEMP_NUM_PBUF 10
#define
MEMP_NUM_TCP_SEG 8
#define
MEMP_NUM_TCP_PCB_LISTEN 1
#define
MEMP_NUM_TCP_PCB 2
#define
MEMP_NUM_UDP_PCB 3
#define
MEMP_NUM_SYS_TIMEOUT 5

#define
MEM_SIZE 1500


Should we use larger PBUF_POOL_SIZE ?  But how
can we be sure that it will work for all types of connections?
Should we use larger HEAP size?
Or if we get unexpected or malformed headers/packets?

Best Regards
/Fredrik