check_ipv4_address may have bug when one progress have different stubs

[ByteXiaoTang]

in sd, check_ipv4_address function, two static should be removed.

because i meet one problem. although i can not understand why.

[ByteXiaoTang]

because i meet one problem. one strange question.

the server send nack, but in fact i have offer event. then i see the following error

stack told me 192.168.3.1 and 192.168.3.4 not in the same subnet. but 192.168.4.1 and 192.168.4.4 have no problem

[ByteXiaoTang]

then ,i remove the two static. static told me 192.168.3.1 and 192.168.3.4 in the same subnet. and server will send sub ack back

[ByteXiaoTang]

in fact. two stubs are alone althougn they in the same progress. and the problems are not inevitable.
just this time, i meet the problem in 3.1.7.1. i can not understand why two static const variable will afact the result and told me 192.168.3.1 and 192.168.3.4 not in the same subnet.