pppd: Be sure to close /dev/ppp when reconnecting (#184)

From https://bugs.debian.org/306261

When using the kernel PPPoE driver, pppd never
closes /dev/ppp when the link has come down.

It opens superfluous fds to the device each time it re-opens the
connection, with the unclosed ones falsely reported always ready for
data by select().

This makes pppd eat up 100% CPU time after the first persist because of
the always instantly returning select() on the unclosed fds.

The problem also occurs with the upstream version, but does not occur
when a pty/tty device is used for the ppp connection.

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Co-authored-by: Simon Peter <dn.tlp@gmx.net>

diff --git a/pppd/sys-linux.c b/pppd/sys-linux.c
index 28bc4be1a689681e400b14bb4d4226898d75e992..587242bb1ed7a2cb0107061a2109e17ccdde1dd1 100644 (file)
--- a/pppd/sys-linux.c
+++ b/pppd/sys-linux.c
@@ -467,6 +467,13 @@ int generic_establish_ppp (int fd)
     if (new_style_driver) {
        int flags;
 
+       /* If a ppp_fd is already open, close it first */
+       if (ppp_fd >= 0) {
+           close(ppp_fd);
+           remove_fd(ppp_fd);
+           ppp_fd = -1;
+       }
+
        /* Open an instance of /dev/ppp and connect the channel to it */
        if (ioctl(fd, PPPIOCGCHAN, &chindex) == -1) {
            error("Couldn't get channel number: %m");