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xu xin
bb48727238
Problem ========= After commit67f6951347("ipv6: Move setting default metric for routes"), we noticed that the logic of assigning the default value of fc_metirc changed in the ioctl process. That is, when users use ioctl(fd, SIOCADDRT, rt) with a non-zero metric to add a route, then they may fail to delete a route with passing in a metric value of 0 to the kernel by ioctl(fd, SIOCDELRT, rt). But iproute can succeed in deleting it. As a reference, when using iproute tools by netlink to delete routes with a metric parameter equals 0, like the command as follows: ip -6 route del fe80::/64 via fe81::5054:ff:fe11:3451 dev eth0 metric 0 the user can still succeed in deleting the route entry with the smallest metric. Root Reason =========== After commit67f6951347("ipv6: Move setting default metric for routes"), When ioctl() pass in SIOCDELRT with a zero metric, rtmsg_to_fib6_config() will set a defalut value (1024) to cfg->fc_metric in kernel, and in ip6_route_del() and the line 4074 at net/ipv3/route.c, it will check by if (cfg->fc_metric && cfg->fc_metric != rt->fib6_metric) continue; and the condition is true and skip the later procedure (deleting route) because cfg->fc_metric != rt->fib6_metric. But before that commit, cfg->fc_metric is still zero there, so the condition is false and it will do the following procedure (deleting). Solution ======== In order to keep a consistent behaviour across netlink() and ioctl(), we should allow to delete a route with a metric value of 0. So we only do the default setting of fc_metric in route adding. CC: stable@vger.kernel.org # 5.4+ Fixes:67f6951347("ipv6: Move setting default metric for routes") Co-developed-by: Fan Yu <fan.yu9@zte.com.cn> Signed-off-by: Fan Yu <fan.yu9@zte.com.cn> Signed-off-by: xu xin <xu.xin16@zte.com.cn> Reviewed-by: David Ahern <dsahern@kernel.org> Link: https://lore.kernel.org/r/20240514201102055dD2Ba45qKbLlUMxu_DTHP@zte.com.cn Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.