skb headroom and tailroom

[Valdis.Kletnieks at vt.edu]

On Wed, 19 Nov 2014 09:43:54 +0530, Varun Sharma said:

> 1. At time of skb allocation sk->sk_prot->max_header value is  272 .
> If we add tcp header+ip header+mac header  outcome  will always less
> than 272 .Then why allocate more ? Is it for future case ?

Did you remember to do the calculation for IPV6 as well as IPv4, and also
to repeat the calculation for the maximum number of IP options (consider an
IPv4 packet that has timestamps, source routing, *and* record route options,
for example - see page 16 of RFC791, and similar for IPv6), and then *also*
the max number of legal TCP option headers?
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