Calling recvfrom() and setsockopt() to add/leave multicast membership from different threads

Question

I have one thread calling recvfrom() and another thread calling setsockopt() to add/leave multicast membership. Is that thread safe or both functions need to be called from the same thread?

Answer 1

These are both system calls, not library functions, so it is safe to call them from different threads.

Whether a join/leave will affect a concurrent recvfrom() that has already started is a moot question.