One of the data structures that holds TCP segments uses an inefficient
algorithm to reassemble the data. This causes the CPU time spent on
segment processing to grow linearly with the number of segments in the
reassembly queue.

As a temporary solution to this problem, these patches limit the size
of each TCP connection's reassembly queue. The value is controlled by
a sysctl (net.inet.tcp.reass.maxqueuelen), which sets the maximum
number of TCP segments that can be outstanding on a session's
reassembly queue. This value defaults to 100.

Note that setting this value too low could impact the throughput of
TCP connections which experience significant loss or
reordering. However, the higher this number is set, the more resources
can be consumed on TCP reassembly processing.

Obtained from: FreeBSD