tested in Emulab test bed
cc@s1:~ % sudo sysctl net.inet.siftr
net.inet.siftr.port_filter: 5001
net.inet.siftr.ppl: 1
net.inet.siftr.logfile: /var/log/siftr.log
net.inet.siftr.enabled: 0
cc@s1:~ % sudo sysctl net.inet.siftr.enabled=1
net.inet.siftr.enabled: 0 -> 1
cc@s1:~ % iperf -c r1 -n 2k -P 2
------------------------------------------------------------
Client connecting to r1, TCP port 5001
TCP window size: 32.0 KByte (default)
------------------------------------------------------------
[ 1] local 10.1.1.2 port 57630 connected with 10.1.1.3 port 5001
[ 2] local 10.1.1.2 port 12504 connected with 10.1.1.3 port 5001
[ ID] Interval Transfer Bandwidth
[ 2] 0.00-0.12 sec 1.95 KBytes 135 Kbits/sec
[ 1] 0.00-0.12 sec 1.95 KBytes 135 Kbits/sec
[SUM] 0.00-0.00 sec 3.91 KBytes 0.000 bits/sec
cc@s1:~ % sudo sysctl net.inet.siftr.enabled=0
net.inet.siftr.enabled: 1 -> 0
cc@s1:~ % cat /var/log/siftr.log
enable_time_secs=1682594224 enable_time_usecs=759909 siftrver=1.3.0 sysname=FreeBSD sysver=1400088 ipmode=4
o,1682594226.996825,10.1.1.2,12504,10.1.1.3,5001,1073725440,1073725440,2,0,0,0,0,2,536,0,1,672,1000000,32768,0,65536,0,0,0,3645937075,63
o,1682594226.996830,10.1.1.2,57630,10.1.1.3,5001,1073725440,1073725440,2,0,0,0,0,2,536,0,1,672,1000000,32768,0,65536,0,0,0,651555559,63
i,1682594227.097091,10.1.1.2,12504,10.1.1.3,5001,1073725440,1073725440,2,0,0,0,0,2,536,0,1,672,1000000,32768,0,65536,0,1,0,3645937075,63
o,1682594227.097104,10.1.1.2,12504,10.1.1.3,5001,1073725440,14480,2,65535,65700,9,9,4,1460,102000,1,16778209,506000,33580,0,65700,0,0,0,3645937075,63
i,1682594227.097107,10.1.1.2,57630,10.1.1.3,5001,1073725440,1073725440,2,0,0,0,0,2,536,0,1,672,1000000,32768,0,65536,0,1,0,651555559,63
o,1682594227.097111,10.1.1.2,57630,10.1.1.3,5001,1073725440,14480,2,65535,65700,9,9,4,1460,102000,1,16778209,506000,33580,0,65700,0,0,0,651555559,63
o,1682594227.097515,10.1.1.2,12504,10.1.1.3,5001,1073725440,14480,2,65535,65700,9,9,4,1460,102000,1,16778208,506000,33580,60,65700,0,0,0,3645937075,63
o,1682594227.097525,10.1.1.2,57630,10.1.1.3,5001,1073725440,14480,2,65535,65700,9,9,4,1460,102000,1,16778208,506000,33580,60,65700,0,0,0,651555559,63
o,1682594227.097539,10.1.1.2,12504,10.1.1.3,5001,1073725440,14480,6,65535,65700,9,9,4,1460,102000,1,16778208,506000,33580,2000,65700,0,60,0,3645937075,63
o,1682594227.097542,10.1.1.2,57630,10.1.1.3,5001,1073725440,14480,6,65535,65700,9,9,4,1460,102000,1,16778208,506000,33580,2000,65700,0,60,0,651555559,63
o,1682594227.097549,10.1.1.2,12504,10.1.1.3,5001,1073725440,14480,6,65535,65700,9,9,6,1460,102000,1,16778208,506000,33580,2000,65700,0,2000,0,3645937075,63
o,1682594227.097551,10.1.1.2,57630,10.1.1.3,5001,1073725440,14480,6,65535,65700,9,9,6,1460,102000,1,16778208,506000,33580,2000,65700,0,2000,0,651555559,63
i,1682594227.198075,10.1.1.2,12504,10.1.1.3,5001,1073725440,14480,6,65535,65700,9,9,6,1460,102000,1,16778224,506000,33580,2000,65700,0,2001,0,3645937075,63
i,1682594227.198088,10.1.1.2,12504,10.1.1.3,5001,1073725440,14540,1030,66048,66048,9,9,6,1460,101875,1,1008,455000,33580,1940,65700,28,1941,0,3645937075,63
i,1682594227.198093,10.1.1.2,57630,10.1.1.3,5001,1073725440,14480,6,65535,65700,9,9,6,1460,102000,1,16778224,506000,33580,2000,65700,0,2001,0,651555559,63
i,1682594227.198098,10.1.1.2,12504,10.1.1.3,5001,1073725440,16480,1030,64512,66020,9,9,6,1460,101781,1,1008,418000,33580,0,65700,0,1,0,3645937075,63
i,1682594227.198104,10.1.1.2,57630,10.1.1.3,5001,1073725440,15988,6,64512,66048,9,9,6,1460,101875,1,1008,455000,33580,492,65700,0,493,0,651555559,63
i,1682594227.198106,10.1.1.2,57630,10.1.1.3,5001,1073725440,16481,6,64512,66048,9,9,9,1460,101781,1,1008,418000,33580,0,65700,0,0,0,651555559,63
i,1682594227.216087,10.1.1.2,12504,10.1.1.3,5001,1073725440,16481,1030,64512,66020,9,9,9,1460,101687,1,1008,389000,33580,0,65700,0,0,0,3645937075,63
o,1682594227.216093,10.1.1.2,12504,10.1.1.3,5001,1073725440,16481,1030,66048,66020,9,9,10,1460,101687,1,1009,389000,33580,0,65700,0,0,0,3645937075,63
i,1682594227.216097,10.1.1.2,57630,10.1.1.3,5001,1073725440,16481,1030,64512,66048,9,9,9,1460,101781,1,1008,418000,33580,0,65700,0,0,0,651555559,63
o,1682594227.216102,10.1.1.2,57630,10.1.1.3,5001,1073725440,16481,1030,66048,66020,9,9,10,1460,101781,1,1009,418000,33580,0,65700,0,0,0,651555559,63
disable_time_secs=1682594229 disable_time_usecs=761095 num_inbound_tcp_pkts=10 num_outbound_tcp_pkts=12 total_tcp_pkts=22 num_inbound_skipped_pkts_malloc=0 num_outbound_skipped_pkts_malloc=0 num_inbound_skipped_pkts_tcpcb=0 num_outbound_skipped_pkts_tcpcb=0 num_inbound_skipped_pkts_inpcb=0 num_outbound_skipped_pkts_inpcb=0 total_skipped_tcp_pkts=0 flowid_list=3645937075,651555559,
Also in IPv6 test:
cc@s1:~ % iperf -Vc fd00::3 -n 2K
------------------------------------------------------------
Client connecting to fd00::3, TCP port 5001
TCP window size: 32.0 KByte (default)
------------------------------------------------------------
[ 1] local fd00::2 port 41237 connected with fd00::3 port 5001
[ ID] Interval Transfer Bandwidth
[ 1] 0.00-0.12 sec 2.00 KBytes 139 Kbits/sec
cc@s1:~ % cat /var/log/siftr.log
enable_time_secs=1682687903 enable_time_usecs=913429 siftrver=1.3.0 sysname=FreeBSD sysver=1400088 ipmode=6
o,1682687905.969819,fd00:0:0:0:0:0:0:2,41237,fd00:0:0:0:0:0:0:3,5001,1073725440,1073725440,2,0,0,0,0,2,1220,0,1,672,1000000,32768,0,65536,0,0,0,1433975434,191
i,1682687906.069816,fd00:0:0:0:0:0:0:2,41237,fd00:0:0:0:0:0:0:3,5001,1073725440,1073725440,2,0,0,0,0,2,1220,0,1,672,1000000,32768,0,65536,0,1,0,1433975434,191
o,1682687906.069828,fd00:0:0:0:0:0:0:2,41237,fd00:0:0:0:0:0:0:3,5001,1073725440,14280,2,65535,66240,9,9,4,1440,101000,1,993,503000,33120,0,66240,0,0,0,1433975434,191
o,1682687906.070234,fd00:0:0:0:0:0:0:2,41237,fd00:0:0:0:0:0:0:3,5001,1073725440,14280,2,65535,66240,9,9,4,1440,101000,1,992,503000,33120,60,66240,0,0,0,1433975434,191
o,1682687906.070260,fd00:0:0:0:0:0:0:2,41237,fd00:0:0:0:0:0:0:3,5001,1073725440,14280,6,65535,66240,9,9,4,1440,101000,1,992,503000,33120,2048,66240,0,60,0,1433975434,191
o,1682687906.070271,fd00:0:0:0:0:0:0:2,41237,fd00:0:0:0:0:0:0:3,5001,1073725440,14280,2,65535,66240,9,9,6,1440,101000,1,992,503000,33120,2048,66240,0,1488,0,1433975434,191
i,1682687906.169817,fd00:0:0:0:0:0:0:2,41237,fd00:0:0:0:0:0:0:3,5001,1073725440,14280,2,65535,66240,9,9,6,1440,101000,1,1008,503000,33120,2048,66240,0,2049,0,1433975434,191
i,1682687906.169822,fd00:0:0:0:0:0:0:2,41237,fd00:0:0:0:0:0:0:3,5001,1073725440,15768,2,65024,66560,9,9,6,1440,100875,1,1008,453000,33120,560,66240,0,561,0,1433975434,191
i,1682687906.169825,fd00:0:0:0:0:0:0:2,41237,fd00:0:0:0:0:0:0:3,5001,1073725440,16329,2,64512,66560,9,9,9,1440,100781,1,1008,416000,33120,0,66240,0,0,0,1433975434,191
i,1682687906.187812,fd00:0:0:0:0:0:0:2,41237,fd00:0:0:0:0:0:0:3,5001,1073725440,16329,1026,64512,66560,9,9,9,1440,100781,1,1008,416000,33120,0,66240,0,0,0,1433975434,191
o,1682687906.187818,fd00:0:0:0:0:0:0:2,41237,fd00:0:0:0:0:0:0:3,5001,1073725440,16329,1026,66560,66532,9,9,10,1440,100781,1,1009,416000,33120,0,66240,0,0,0,1433975434,191
disable_time_secs=1682687908 disable_time_usecs=951733 num_inbound_tcp_pkts=5 num_outbound_tcp_pkts=6 total_tcp_pkts=11 num_inbound_skipped_pkts_malloc=0 num_outbound_skipped_pkts_malloc=0 num_inbound_skipped_pkts_tcpcb=0 num_outbound_skipped_pkts_tcpcb=0 num_inbound_skipped_pkts_inpcb=0 num_outbound_skipped_pkts_inpcb=0 total_skipped_tcp_pkts=0 flowid_list=1433975434,