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We need a real-time notification for tcp retransmission for monitoring. Of course we could use ftrace to dynamically instrument this kernel function too, however we can't retrieve the connection information at the same time, for example perf-tools [1] reads /proc/net/tcp for socket details, which is slow when we have a lots of connections. Therefore, this patch adds a tracepoint for __tcp_retransmit_skb() and exposes src/dst IP addresses and ports of the connection. This also makes it easier to integrate into perf. Note, I expose both IPv4 and IPv6 addresses at the same time: for a IPv4 socket, v4 mapped address is used as IPv6 addresses, for a IPv6 socket, LOOPBACK4_IPV6 is already filled by kernel. Also, add sk and skb pointers as they are useful for BPF. 1. https://github.com/brendangregg/perf-tools/blob/master/net/tcpretrans Cc: Eric Dumazet <edumazet@google.com> Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com> Cc: Hannes Frederic Sowa <hannes@stressinduktion.org> Cc: Brendan Gregg <brendan.d.gregg@gmail.com> Cc: Neal Cardwell <ncardwell@google.com> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Brendan Gregg <bgregg@netflix.com> Signed-off-by: David S. Miller <davem@davemloft.net> |
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| fs | ||
| include | ||
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| ipc | ||
| kernel | ||
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| samples | ||
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| tools | ||
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README
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.