Query on skb buffer

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