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Inability to bind socket when user ip is set for ethernet adapter

Problem

In our system, working with RTEMS 4.9.2, we are faced with a very complex socket problem. We install the socket and use the following command to bind:

// Bind the socket to set the local port sockaddr_in localSocketAddress = {0}; localSocketAddress.sin_family = AF_INET; localSocketAddress.sin_port = (u_short)localPort; localSocketAddress.sin_addr.s_addr = localAddress; if (bind( mSocket, (sockaddr *)&localSocketAddress, sizeof(sockaddr_in)) == SOCKET_ERROR) { int errorOut = errno; ...

And this works for UDP communications, with the exception of a strange specific scenario, which is explained below. The problem we are facing is that this bind call fails, even if the setting is correct. We get error 125 , which for RTEMS EADDRNOTAVAIL :

The requested non-existent interface or the requested address was not local.

Obvious reason

When loading the device, we can configure our network in one of 2 ways:

  • Network IP and SUBNET are automatically configured based on what is in the default bootloader (UBOOT), and configured through the RTEMS OS.

  • The RTEMS rtems_bsdnet_ifconfig function is called to change the IP address of a single Ethernet interface after boot.

For clarification, option 2 is called:

 rtems_bsdnet_ifconfig(eth_interface, SIOCSIFADDR, &ipaddr);

If the network is configured as specified in option 1, everything works as expected, but if option 2 is used (even if the setting matches the network options defined by option 1), the socket binding failed.

Is there a known cause or error for RTEMS that indicates that this binding will fail if you reconfigure your IP address?

Additional Information

  • We configure a new IP address (option 2) using a method that essentially uses ioctl("eht1", SIOCSIFADDR, ...) .

  • If we bind our socket without specifying a local ADDRESS (i.e. use INADDR_ANY ), then it works anyway.

  • rtems_bsdnet_ifconfig is a simple interface for the ioctl function. This is from rtems_glue.c and has a function signiture int rtems_bsdnet_ifconfig(const char *ifname, uint32_t cmd, void *param)

  • All the usual network functions seem to work, except for this binding.

  • After watching this, I thought that I needed to do more to reset my IP address. But this does not work, using the first answer or even doing something with SIOCSIFFLAGS , leads to the termination of all network functions.

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1 answer

You did not specify the architecture you are working on, but you set the port and address in local byte order, which may not match the network byte order. The very first thing I will try:

localSocketAddress.sin_port = htons (localPort); localSocketAddress.sin_addr.s_addr = htonl (localAddress);

It will also make your code more portable, in case it is NOT your problem (that is, you work on a large end hosting), and one day you will try to compile another system that is a little oriented.

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