Query on skb buffer

[Kumar amit mehta]

My current understanding is that the skb, while being passed along various
layers in linux network stack, will be manipulated majorly, using the
skb->{head|data|tail|end|len} fields. 

Suppose that my application (say 'ping') sends a ICMP echo request with a
large packet size of 4k, i.e. $ ping -s 4096 <dest addr>
Now, if alloc_skb(4096, GFP_KERNEL) is the routine that gets called to allocate
the kernel buffer then, how does the kernel manages such prospective memory 
allocation failures and how kernel manages large packet requests from the
application.

-Amit