Hi there, I've been writing applications that need local interface information several times now (IP-address, MAC, subnet mask, ARP, routing info etc.), for different versions of the Linux kernel. Every time I have to implement such a routine I find myself wondering what interface will be 'the best'. The /proc filesystem? The sysfs filesystem? IOCTL's? NETLINK sockets? Of course, they all work most of the time; but not for all Linux versions. Let's take an issue I've had; get the interface name using a given MAC-address. I could use IOCTL's, this method probably produces the most readable code, works with practically every Linux kernel and is relatively easy to implement. First get interface information using SIOCGIFCONF, then iterate through the list and call SIOCGIFHWADDR to get the MAC-addresses. However, SIOCGIFCONF does not return interface information of interfaces that have no IP-address, so this method was rejected due to the need for this capability. The NETLINK implementation seemed rather hefty (in terms of codesize and readability) so was not preferred. Then I used the /proc filesystem interface; this was pretty doable, but still I somehow always question the sensibility of the dissecting-info-from-formatted-files-method to read the interface names from /proc/net/dev. This seemed to work fine, and worked with all kernel versions.... ...until Linux-2.6.25 was released, where /proc/net is changed to be a symlink to /proc/self/net and a symlink-check in the application made the application somewhat disfunctional. The check was put there to make sure the /proc/net directory was not rerouted by a symlink (with possible malicious intentions). A simple removal of the check was the solution, bringing along all possible security compromises. This example was given to indicate the issues I come across all the time, not as a specific problem or something. I've been reading a lot about kernel interfaces but there always seems to be a dispute about which one is appropriate for a particular situation. But no matter how much I learn about the different interfaces, I still have trouble choosing the 'right' one. My question is, is there some general rule-of-thumb you use that could help me on this? Or any other type of advice? Any methods you use to decide? Any help is appreciated! Thanks in advance! -Kris -- To unsubscribe from this list: send the line "unsubscribe linux-net" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
