- fix regression introduced in fping 4.3

[dinoex]

bind to source only when option was set.
this allows to work in jails and lxc with custom IPs.
this allows IPv4 only and IPv6 only hosts

[coveralls]

Coverage decreased (-0.02%) to 81.668% when pulling 31f76f6 on dinoex:develop into 296de3d on schweikert:develop.

[frenchie]

More info is available on the FreeBSD bug report, Comment 7.

Regression introduced by commit 1486bf2.

[dinoex]

Coverage decreased is expected.
with this patch we only bind with the address family in use, not both.

[tohojo]

This seems to have broken fping on Linux (Arch Linux 5.11 running as a local user):

$ git reset --hard origin/develop
HEAD is now at eac20347bac9 Merge pull request #200 from simetnicbr/for-upstream/privileged-SO_BINDTODEVICE
$ make
/usr/bin/make  all-recursive
make[1]: Entering directory '/home/build/git/fping'
Making all in doc
make[2]: Entering directory '/home/build/git/fping/doc'
make[2]: Nothing to be done for 'all'.
make[2]: Leaving directory '/home/build/git/fping/doc'
Making all in src
make[2]: Entering directory '/home/build/git/fping/src'
gcc -DHAVE_CONFIG_H -I. -I..    -Wall -Wextra -Wno-sign-compare -DIPV6 -g -O2 -MT fping-fping.o -MD -MP -MF .deps/fping-fping.Tpo -c -o fping-fping.o `test -f 'fping.c' || echo './'`fping.c
mv -f .deps/fping-fping.Tpo .deps/fping-fping.Po
gcc -Wall -Wextra -Wno-sign-compare -DIPV6 -g -O2   -o fping fping-fping.o fping-seqmap.o fping-socket4.o fping-optparse.o fping-socket6.o  
make[2]: Leaving directory '/home/build/git/fping/src'
make[2]: Entering directory '/home/build/git/fping'
make[2]: Nothing to be done for 'all-am'.
make[2]: Leaving directory '/home/build/git/fping'
make[1]: Leaving directory '/home/build/git/fping'
$ ./src/fping -D -c 1 127.0.0.1 -z 1
./src/fping:
  count: 1, retry: 3, interval: 10 ms
  perhost_interval: 1000 ms, timeout: 1000
  ping_data_size = 56, trials = 4
  count_flag set
  backoff_flag set
  per_recv_flag set
[1616254202.57978] 127.0.0.1 [0]: add ping event in 0 ms
[1616254202.57978] # main_loop
[1616254202.57978] 127.0.0.1 [0]: ping event
[1616254202.57989] seqmap_add(host: 0, index: 0) -> 0
[1616254202.57989] 127.0.0.1 [0]: send ping
[1616254202.57989] 127.0.0.1 [0]: add timeout event in 1000 ms
[1616254202.57989] next timeout event in 1000 ms (127.0.0.1)
[1616254202.57989] waiting up to 1000 ms
[1616254202.58004] # main_loop
[1616254202.58004] next timeout event in 1000 ms (127.0.0.1)
[1616254202.58004] waiting up to 1000 ms
[1616254203.58102] # main_loop
[1616254203.58102] 127.0.0.1 [0]: timeout event
[1616254203.58102] 127.0.0.1 : [0], timed out (NaN avg, 100% loss)

127.0.0.1 : xmt/rcv/%loss = 1/0/100%
1 $ git revert 31f76f607158
Auto-merging src/fping.c                       
[develop 191adae5a42b] Revert "- fix regression introduced in fping 4.3"
 1 file changed, 2 insertions(+), 2 deletions(-)
$ make
/usr/bin/make  all-recursive
make[1]: Entering directory '/home/build/git/fping'
Making all in doc
make[2]: Entering directory '/home/build/git/fping/doc'
make[2]: Nothing to be done for 'all'.
make[2]: Leaving directory '/home/build/git/fping/doc'
Making all in src
make[2]: Entering directory '/home/build/git/fping/src'
gcc -DHAVE_CONFIG_H -I. -I..    -Wall -Wextra -Wno-sign-compare -DIPV6 -g -O2 -MT fping-fping.o -MD -MP -MF .deps/fping-fping.Tpo -c -o fping-fping.o `test -f 'fping.c' || echo './'`fping.c
mv -f .deps/fping-fping.Tpo .deps/fping-fping.Po
gcc -Wall -Wextra -Wno-sign-compare -DIPV6 -g -O2   -o fping fping-fping.o fping-seqmap.o fping-socket4.o fping-optparse.o fping-socket6.o  
make[2]: Leaving directory '/home/build/git/fping/src'
make[2]: Entering directory '/home/build/git/fping'
make[2]: Nothing to be done for 'all-am'.
make[2]: Leaving directory '/home/build/git/fping'
make[1]: Leaving directory '/home/build/git/fping'
$ ./src/fping -D -c 1 127.0.0.1 -z 1
./src/fping:
  count: 1, retry: 3, interval: 10 ms
  perhost_interval: 1000 ms, timeout: 1000
  ping_data_size = 56, trials = 4
  count_flag set
  backoff_flag set
  per_recv_flag set
[1616254232.26669] 127.0.0.1 [0]: add ping event in 0 ms
[1616254232.26669] # main_loop
[1616254232.26669] 127.0.0.1 [0]: ping event
[1616254232.26677] seqmap_add(host: 0, index: 0) -> 0
[1616254232.26677] 127.0.0.1 [0]: send ping
[1616254232.26677] 127.0.0.1 [0]: add timeout event in 1000 ms
[1616254232.26677] next timeout event in 1000 ms (127.0.0.1)
[1616254232.26677] waiting up to 1000 ms
[1616254232.26689] seqmap_fetch(0) -> host: 0, index: 0
[1616254232.26689] received [0] from 127.0.0.1
[1616254232.26689] 127.0.0.1 : [0], 64 bytes, 0.124 ms (0.124 avg, 0% loss)

127.0.0.1 : xmt/rcv/%loss = 1/1/0%, min/avg/max = 0.124/0.124/0.124