From: Ido Schimmel <ido...@mellanox.com> So far drop monitor supported only one mode of operation in which a summary of recent packet drops is periodically sent to user space as a netlink event. The event only includes the drop location (program counter) and number of drops in the last interval.
While this mode of operation allows one to understand if the system is dropping packets, it is not sufficient if a more detailed analysis is required. Both the packet itself and related metadata are missing. This patchset extends drop monitor with another mode of operation where the packet - potentially truncated - and metadata (e.g., drop location, timestamp, netdev) are sent to user space as a netlink event. Thanks to the extensible nature of netlink, more metadata can be added in the future. To avoid performing expensive operations in the context in which kfree_skb() is called, the dropped skbs are cloned and queued on per-CPU skb drop list. The list is then processed in process context (using a workqueue), where the netlink messages are allocated, prepared and finally sent to user space. As a follow-up, I plan to integrate drop monitor with devlink and allow the latter to call into drop monitor to report hardware drops. In the future, XDP drops can be added as well, thereby making drop monitor the go-to netlink channel for diagnosing all packet drops. Example usage with patched dropwatch [1] can be found here [2]. Example dissection of drop monitor netlink events with patched wireshark [3] can be found here [4]. I will submit both changes upstream after the kernel changes are accepted. Patches #1-#6 are just cleanups with no functional changes intended. Patches #7-#8 perform small refactoring before the actual changes are introduced in the last four patches. [1] https://github.com/idosch/dropwatch/tree/packet-mode [2] https://gist.github.com/idosch/7391b77da0b16182406189561fdfa1ef#file-gistfile1-txt [3] https://github.com/idosch/wireshark/tree/drop-monitor [4] https://gist.github.com/idosch/7391b77da0b16182406189561fdfa1ef#file-gistfile2-txt Ido Schimmel (12): drop_monitor: Use correct error code drop_monitor: Rename and document scope of mutex drop_monitor: Document scope of spinlock drop_monitor: Avoid multiple blank lines drop_monitor: Add extack support drop_monitor: Use pre_doit / post_doit hooks drop_monitor: Split tracing enable / disable to different functions drop_monitor: Initialize timer and work item upon tracing enable drop_monitor: Require CAP_NET_ADMIN for drop monitor configuration drop_monitor: Add packet alert mode drop_monitor: Allow truncation of dropped packets drop_monitor: Add a command to query current configuration include/uapi/linux/net_dropmon.h | 33 +++ net/core/drop_monitor.c | 492 ++++++++++++++++++++++++++++--- 2 files changed, 478 insertions(+), 47 deletions(-) -- 2.21.0
