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Tom Parkin says: ==================== add ppp_generic ioctl(s) to bridge channels Following on from my previous RFC[1], this series adds two ioctl calls to the ppp code to implement "channel bridging". When two ppp channels are bridged, frames presented to ppp_input() on one channel are passed to the other channel's ->start_xmit function for transmission. The primary use-case for this functionality is in an L2TP Access Concentrator where PPP frames are typically presented in a PPPoE session (e.g. from a home broadband user) and are forwarded to the ISP network in a PPPoL2TP session. The two new ioctls, PPPIOCBRIDGECHAN and PPPIOCUNBRIDGECHAN form a symmetric pair. Userspace code testing and illustrating use of the ioctl calls is available in the go-l2tp[2] and l2tp-ktest[3] repositories. [1]. Previous RFC series: https://lore.kernel.org/netdev/20201106181647.16358-1-tparkin@katalix.com/ [2]. go-l2tp: a Go library for building L2TP applications on Linux systems. Support for the PPPIOCBRIDGECHAN ioctl is on a branch: https://github.com/katalix/go-l2tp/tree/tp_002_pppoe_2 [3]. l2tp-ktest: a test suite for the Linux Kernel L2TP subsystem. Support for the PPPIOCBRIDGECHAN ioctl is on a branch: https://github.com/katalix/l2tp-ktest/tree/tp_ac_pppoe_tests_2 Changelog: v4: * Fix NULL-pointer access in PPPIOCBRIDGECHAN in the case that the ID of the channel to be bridged wasn't found. * Add comment in ppp_unbridge_channels to better document the unbridge process. v3: * Use rcu_dereference_protected for accessing struct channel 'bridge' field during updates with lock 'upl' held. * Avoid race in ppp_unbridge_channels by ensuring that each channel in the bridge points to it's peer before decrementing refcounts. v2: * Add missing __rcu annotation to struct channel 'bridge' field in order to squash a sparse warning from a C=1 build * Integrate review comments from gnault@redhat.com * Have ppp_unbridge_channels return -EINVAL if the channel isn't part of a bridge: this better aligns with the return code from ppp_disconnect_channel. * Improve docs update by including information on ioctl arguments and error return codes. ==================== Reviewed-by: Guillaume Nault <gnault@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel
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