[5/*] [IPSEC] Use dst_mtu in xfrm[46]_output

[Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>]

There was a lot of fun in laying the foundations.  Now it's time
to start using it.

This patch fixes the calculations in xfrm[46]_output so that we don't
reject properly sized packets from the TCP stack.  The previous
calculation is wrong because the xfrm overhead is not constant.

Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>

After this I'll start cleaning stuff up.  For example, tcp's
ext2_header_len and dst's path can both be removed.

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@xxxxxxxxxxxxxxxxxxx>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

xfrm-5
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