Should the values set with setsockopt stay valid during lifetime of the socket?-CodePudding

I'm trying to create helper functions to setup the keep alive of a tcp socket. The setsockopt function accepts a pointer to a value. My question is, does the value have to stay valid for the entire lifetime of the socket or only while executing this function?

This is the example I use: https://github.com/espressif/esp-idf/blob/ac315adc2c76309b8b9c82e166f03891ad2031bb/examples/protocols/sockets/tcp_server/main/tcp_server.c

To clarify my question, which of the following examples would be correct?

Example 1:

void SetKeepAlive(int handle, int enable, int idle, int interval, int count)
{
    // Set tcp keepalive option
    setsockopt(handle, SOL_SOCKET, SO_KEEPALIVE, &enable, sizeof(int));
    setsockopt(handle, IPPROTO_TCP, TCP_KEEPIDLE, &idle, sizeof(int));
    setsockopt(handle, IPPROTO_TCP, TCP_KEEPINTVL, &interval, sizeof(int));
    setsockopt(handle, IPPROTO_TCP, TCP_KEEPCNT, &count, sizeof(int));
}

Example 2:

int _enable;
int _idle;
int _interval;
int _count;
    
void SetKeepAlive2(int handle, int enable, int idle, int interval, int count)
{
    _enable     = enable;
    _idle       = idle;
    _interval   = interval;
    _count      = count;

    // Set tcp keepalive option
    setsockopt(handle, SOL_SOCKET, SO_KEEPALIVE,    &_enable, sizeof(int));
    setsockopt(handle, IPPROTO_TCP, TCP_KEEPIDLE,   &_idle, sizeof(int));
    setsockopt(handle, IPPROTO_TCP, TCP_KEEPINTVL,  &_interval, sizeof(int));
    setsockopt(handle, IPPROTO_TCP, TCP_KEEPCNT,    &_count, sizeof(int));
}

CodePudding user response：

The parameter to setsockopt is not expected to persist forever, and would be copied by the call.

Note, though, that this might not extend to anything a socket option might point to (though the only cases I did find (SO_ATTACH_FILTER/SO_ATTACH_REUSEPORT_CBPF) do copy the internally pointed to object, and it's reasonable to expect most similar cases to behave the same).

I would generally expect anything requiring an extended lifetime to be documented as such.