On Thu, Sep 14, 2000 at 11:06:33AM -0400, Tony Willoughby wrote: > > Are there any known issues with /proc/net/route? It seems that > reading /proc/net/route doesn't always return all of the routes in the > routing table. > > I'm writing a user-space program (that runs as root) that will go > through the routing table and delete routes with a specific gateway. > It opens /proc/net/route and reads each line by calling fgets() in a > loop until fgets() returns NULL. > > Almost always, when there are several (more than 30 or so), routes in > the table fgets() returns NULL before all of the routes have been > read. Subsequent executions of this program will delete some (or all) > of the remaining routes. If the program is run enough times all of > the desired routes will be deleted. > > The algorithm for reading/parsing the contents of /proc/net/route is > loosely based on netstat.c from net-tools-1.53. > > I'm running 2.2.14-12. A Red Hat distribution. > > Is anyone aware of any problems with /proc/net/route? Read all routes in first and then delete them in a single go. Background: /proc works with 4K buffers. When you read an offset >4K it computes the old route and just doesn't supply the routes that would end < your seek offset. When you're deleting routes inbetween the routes will shift down in the list and you're effectively skipping routes when you cross a 4K boundary. This is a fundamental design problem in /proc and probably not fixable. Note that /proc/net/route does not display the full routing table anyways, if you want all the details you need to use netlink/rtnetlink (see their man pages). rtnetlink still has the same problem though, because real cursors for the FIB would be too complex to manage. -Andi - : send the line "unsubscribe linux-net" in the body of a message to majordomo@vger.kernel.org
