How can I specify that a socket use a specific interface?
If I have a wi-fi connection to one network and a cat5 connection to another, how can i tell my socket to route through a specific one (and not even try the other)?
To be clear, I'm talking about an outgoing connection. For example, I use send() a few lines after what is shown here to send a web request and recv() to get the requested page. The catch being that I need to specify that the request be routed through a specific interface, not just any old interface (assuming that at runtime there are 2 or more available connections from the computer out to the internet).
I thought it was bind() that did this, but it doesn't seem like that's what it's doing at all. I have a book that led me to believe bind() would tell a socket to route through a specific interface (thus BINDing it to the socket), but I think it's more likely that it's a dns-related call. unfortunately, the man page is strangely ambiguous about what it actually does, using the word 'name' a lot, but never actually saying 'hostname'.
In any case, here's the code i've got that isn't working (although I'm pretty sure the setsockopt() line is okay) :
// setup local address stuff...
struct sockaddr_in LOCaddr; LOCaddr.sin_family = AF_INET; LOCaddr.sin_addr.s_addr = inet_addr(local_ip);
// set to true for SO_DONTROUTE...
int val = 1;
// bind to specific interface and then set SO_DONTROUTE...
if (bind(sockethandle, (struct sockaddr *)&LOCaddr, sizeof(LOCaddr))==0) {
setsockopt(sockethandle, SOL_SOCKET, SO_DONTROUTE, &val, sizeof(val));
}
What do I need to do here instead of bind()?
Thanks.
- Philip
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