mirror of
https://github.com/xdp-project/bpf-examples.git
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7410d5cc2c
Perform various fixes and tweaks: - Rename several defines to make them more informative - Remove unrolling of loop in BPF programs - Reuse defines for program sections between userspace and kernel space programs - Perform fork+exec to run bpf_egress_loader script instead of system() - Add comment to copied scripts indicating I've modified them - Add pping.h and pping_helpers.h as dependencies in Makefile Also, add a brief description of what PPing is and how it works to README Signed-off-by: Simon Sundberg <simon.sundberg@kau.se>
20 lines
1.2 KiB
Markdown
20 lines
1.2 KiB
Markdown
# PPing using XDP and TC-BPF
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An implementation of the passive ping ([pping](https://github.com/pollere/pping)) utility based on XDP (for ingress) and TC-BPF (for egress)
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## Simple description
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Passive Ping (PPing) makes use of the TCP Timestamp option to calculate the RTT for TCP traffic passing through.
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PPing can be used on measure RTTs on end hosts or any device which sees both directions of the TCP flow.
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For outgoing packets, it checks for TCP timestamp TSval in the TCP header. If it finds one it creates a timestamp
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for when it saw that TSval in a particular flow. On incomming packets it parses the TCP timestamp TSecr (which
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is the TSval echoed by the receiving host) and checks it has seen any previous outgoing packets with that TCP
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timestamp. If it has, an RTT is calculated as the difference in time between when it saw an outgoing packet
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with a TSval, and when it received an incomming packet from the reverse flow with a matching TSecr.
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Note that TCP timestamps may not be unique for every packet in a flow, therefore it only matches the first
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outgoing packet with a particular TSval with the first incomming packet with a matching TSecr. Duplicate
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TSval/TSecr are ignored.
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## Planned design
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