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How can I bind a socket to a particular network interface? I tried using setsockopt on server side, but the clients can still access the service through both eth0 and lo interfaces.
I can achieve this by setting the particular IP address using serv_addr.sin_addr.s_addr.
But I suspect that we can bind to an interface using only setsockopt (without mentioning the IP address).
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s_addr = inet_addr("9.1.2.3"); int rc = bind(sd, (struct sockaddr *)&serveraddr, sizeof(serveraddr)); Show activity on this post. In bind_using_iface_ip , to bind to any port 0 should be passed. And also if the fd is raw socket then need to pass port as 0 .
An application must use recvfrom to read datagrams from a raw socket. Before you can receive packets on a raw socket, you must bind the socket to the IP address of the interface on which you want to receive packets.
When a socket has both an IP address and a port number it is said to be 'bound to a port', or 'bound to an address'. A bound socket can receive data because it has a complete address. The process of allocating a port number to a socket is called 'binding'.
Use Linux SO_BINDTODEVICE and mac IP_BOUND_IF / IPV6_BOUND_IF to bind socket to a network interface In Linux, SO_BINDTODEVICE is a socket option can be used in setsockopt () to bind a socket to network interface. e.g. Bind this socket to a particular device like “eth0”, as specified in the passed interface name.
Bind your service incoming traffic only to a dedicated interface. If you need to bind more than one interface using the built-in socket module, create multiple sockets (instead of binding to one socket to all interfaces).
When you bind the port to all interfaces using 0.0.0.0 as the IP address, you essentially allow it to accept connections from any IPv4 address provided that it can get to the socket via routing. Binding to all interfaces is therefore associated with security risks.
In bind_using_iface_ip, to bind to any port 0 should be passed. And also if the fd is raw socket then need to pass port as 0. This bind mechanism is common for all kind of sockets like raw, dgram and stream. Thanks for contributing an answer to Stack Overflow!
You can bind to a specific interface by setting SO_BINDTODEVICE socket option.
struct ifreq ifr; memset(&ifr, 0, sizeof(ifr)); snprintf(ifr.ifr_name, sizeof(ifr.ifr_name), "eth0"); if (setsockopt(s, SOL_SOCKET, SO_BINDTODEVICE, (void *)&ifr, sizeof(ifr)) < 0) { ... error handling ... } Warning: You have to be root and have the CAP_NET_RAW capability in order to use this option.
The second method is that you can resolv IP address tied to an interface with getifaddrs().
Follow the latter link for a comprehensive example.
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The only way you can do it is as you mention -
by setting the particular IP address using
serv_addr.sin_addr.s_addr
You can't do it without knowing the address to bind to.
You can use ioctls to determine the current IP address if you need, though there may be a cleverer way to do this these days - I've not done much in modern Linux distros lately.
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