twping disregards twamp server config for source port

[igarny]

Hi Mark, guys,

>> twping --help 2>&1 | grep Version
Version: 4.4.0-1

>> grep ports /etc/twamp-server/twamp-server.conf
" # keep this on, and help us with more specific bug reports!
testports 18760-19960

Test shows use of OWAMP test ports for SOURCE port

>> twping -s 1000 -c 100 -S 131.188.81.82 -4 vm02-perf.slough.ja.net
twping: NTP: STA_NANO should be set. Make sure ntpd is running, and your NTP configuration is good.
Approximately 13.1 seconds until results available

--- twping statistics from [t2-psdev.rrze.uni-erlangen.de]:9488 to [vm02-perf.slough.ja.net]:19547 ---
SID: c25112f5e461ed3d47277e2f4333e118
first: 2021-06-02T13:42:54.519
last: 2021-06-02T13:43:04.383
100 sent, 0 lost (0.000%), 0 send duplicates, 0 reflect duplicates
round-trip time min/median/max = 19.4/19.8/21.8 ms, (err=0.331 ms)
send time min/median/max = 9.6/9.9/11 ms, (err=0.166 ms)
reflect time min/median/max = 9.73/9.9/12 ms, (err=0.166 ms)
reflector processing time min/max = 0.00715/0.145 ms
two-way jitter = 0.2 ms (P95-P50)
send jitter = 0.2 ms (P95-P50)
reflect jitter = 0.1 ms (P95-P50)
send hops = 12 (consistently)
reflect hops = 12 (consistently)

I would expect to see something like this, where SOURCE port corresponds to the TWAMP pool of UDP ports, not the one for OWAMP.
>> twping -P 18760-19960 -s 1000 -c 100 -S 131.188.81.82 -4 psmp-gn-owd-02.fra.de.geant.net
twping: NTP: STA_NANO should be set. Make sure ntpd is running, and your NTP configuration is good.
Approximately 13.0 seconds until results available

--- twping statistics from [t2-psdev.rrze.uni-erlangen.de]:19778 to [psmp-gn-owd-02.fra.de.geant.net]:19778 ---
SID: 3e286a51e461f83b1b8f041461cc6ca7
first: 2021-06-02T14:29:48.130
last: 2021-06-02T14:29:57.519
100 sent, 0 lost (0.000%), 0 send duplicates, 0 reflect duplicates
round-trip time min/median/max = 4.08/4.3/4.43 ms, (err=0.0963 ms)
send time min/median/max = 1.67/1.8/1.84 ms, (err=0.0482 ms)
reflect time min/median/max = 2.38/2.5/2.72 ms, (err=0.0482 ms)
reflector processing time min/max = 0.00191/0.02 ms
two-way jitter = 0.1 ms (P95-P50)
send jitter = 0 ms (P95-P50)
reflect jitter = 0.1 ms (P95-P50)
send hops = 6 (consistently)
reflect hops = 6 (consistently)