8c1bd9b6a5
Backport patches improving ppp interface creation. As a side effect this also fix a bug from using netdev trigger that suffer from LED state wrongly set due to using old ioctl for ppp creation. Tested-by: Csaba Sipos <metro4@freemail.hu> Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
59 lines
2.1 KiB
Diff
59 lines
2.1 KiB
Diff
From 44609bfc974bdafc0316d069aabf5e2903efa805 Mon Sep 17 00:00:00 2001
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From: pali <7141871+pali@users.noreply.github.com>
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Date: Tue, 9 Aug 2022 11:20:15 +0200
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Subject: [PATCH] pppd: Workaround for generating ppp unit id on Linux (#355)
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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Linux kernel has nasty bug / feature. If PPPIOCNEWUNIT is called with
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negative ppp unit id (which is default option when command line argument
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"unit" is not specified; and tells kernel to choose some free ppp unit id)
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and the lowest unused/free ppp unit id is present in some existing network
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interface name prefixed by "ppp" string then this PPPIOCNEWUNIT ioctl
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fails. In this case kernel is basically unable to create a new ppp
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interface via PPPIOCNEWUNIT ioctl when user does not specify some unused
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and non-conflicted unit id.
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Linux kernel should be fixed to choose usable ppp unit id when was
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requested via PPPIOCNEWUNIT parameter -1.
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Until this happens, add a workaround for pppd to help choosing some random
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ppp unit id when kernel returns this error.
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Simple test case (run on system when there is no ppp interface):
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sudo ./pppd ifname ppp1 nodefaultroute noauth nolock local nodetach pty "./pppd nodefaultroute noauth nolock local nodetach notty"
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Second pppd process without this patch prints into syslog following error:
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pppd 2.4.10-dev started by pali, uid 0
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Couldn't create new ppp unit: File exists
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Exit.
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With this patch it falls back to random ppp unit id and succeeds:
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pppd 2.4.10-dev started by pali, uid 0
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Using interface ppp1361
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Connect: ppp1361 <--> /dev/pts/14
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...
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Signed-off-by: Pali Rohár <pali@kernel.org>
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---
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pppd/sys-linux.c | 5 +++++
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1 file changed, 5 insertions(+)
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--- a/pppd/sys-linux.c
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+++ b/pppd/sys-linux.c
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@@ -873,6 +873,11 @@ static int make_ppp_unit(void)
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ifunit = -1;
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x = ioctl(ppp_dev_fd, PPPIOCNEWUNIT, &ifunit);
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}
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+ if (x < 0 && errno == EEXIST) {
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+ srand(time(NULL) * getpid());
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+ ifunit = rand() % 10000;
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+ x = ioctl(ppp_dev_fd, PPPIOCNEWUNIT, &ifunit);
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+ }
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if (x < 0)
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error("Couldn't create new ppp unit: %m");
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