Only allowing four missing packets is hurting
performance for large receive windows.
The new value was picked by observing good
performance with 500 kB socket buffers.
Closes: #264
Approved by: whitequark
The current hole was always shrinked even if the
packet assembler rejected adding a packet due to
not being able to insert a new hole.
Shrink only after a new hole was added.
Shrinking before or after does not make a difference
because offset + size < hole_size and thus
contigs[index] is not empty, passing the
debug_assert in add_contig_at.
https://github.com/m-labs/smoltcp/issues/261Closes: #265
Approved by: whitequark