Upcoming EuroBSDCon OpenBSD talk A Packet's Journey Through the OpenBSD Network Stack by Alexander Bluhm
Upcoming EuroBSDCon OpenBSD talk A Packet's Journey Through the OpenBSD Network Stack by Alexander Bluhm
Upcoming EuroBSDCon OpenBSD talk A Packet's Journey Through the OpenBSD Network Stack by Alexander Bluhm
When debugging network issues, it is important to understand when
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certain things happen. Tcpdump provides valuable insight, pf
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transforms packets, pseudo devices add features, and netstat counters
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show action. The call graph of the functions within the kernel is
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the base to comprehend the relation between these sources of
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information.
The layering of kernel code in hardware drivers, pseudo devices,
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IP processing, forwarding and protocol layer is explained. The
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kernel provides the socket interface to userland processes. Packet
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forwarding happens within the kernel. Bridge code uses certain
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shortcuts. pf is a swiss knife that can manipulate traffic in
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multiple layers. IPsec has an independent interface that overrides
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routing. Routing itself and neighbor discovery is a necessary step
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that has its tentacles everywhere. Checksum calculation can be
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performed by hardware offloading.
By using examples with a single packets, their way through the
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kernel is shown. The possible branches, configuration options, and
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measurement output are put in correlation.
Tickets are still available and this talk will be streamed and recorded for later release.