Increase FT_SO_RCV_BUFSIZE from 4Mb to 8

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On large netflow flows (e.g. >800Mbit/sec) we constantly see following in logs:
Jan  3 12:12:00 radius-minsk2 flow-capture[98939]: STAT: now=1325581920 
startup=1324649629 src_ip=172.16.2.23 dst_ip=172.16.2.50 d_ver=5 pkts=77674720 
flows=2330241600 lost=22560 reset=3 filter_drops=0

In the same time udp dgrams dropped due to no socjet and due to full socket 
constanly increases: 

[gawriloff@radius-minsk2 /usr/home/gawriloff]$ netstat -s -p udp
udp:
        1378886026 datagrams received
        0 with incomplete header
        0 with bad data length field
        0 with bad checksum
        20888 with no checksum
        71766750 dropped due to no socket
        65910 broadcast/multicast datagrams undelivered
        43841072 dropped due to full socket buffers

Recv-Q on flow-capture is always non-zero:

[gawriloff@radius-minsk2 /usr/home/gawriloff]$ sudo netstat -na | grep udp4  
866304      0 *.2074                 *.*

[gawriloff@radius-minsk2 /usr/home/gawriloff]$ ps ugaxww | grep 2074
root       98945 96.0  0.0 12428  1868  ??  Rs   23Dec11 6227:38.04 
/usr/local/bin/flow-capture -w /var/netflow/flows/rtr10 -n 1439 -b big -z 9 -p 
/var/run/flow-capture.pid -N 0 -V 5 -S 1 0/0/2074

So I propose to increase  FT_SO_RCV_BUFSIZE from 4Mb to 8 in ftlib.h or better 
make it configurable through addition parameter.
For example: 
-sock 8Mb

Original issue reported on code.google.com by [email protected] on 3 Jan 2012 at 9:17