XDP: Difference between revisions

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* <tt>XDP_TX</tt>: emit the packet back out the interface on which it was received

* <tt>XDP_REDIRECT</tt>: send the packet to another NIC or an <tt>AF_XDP</tt> socket

Think of <tt>XDP_ABORTED</tt> as returning -1 from the eBPF program; it's meant to indicate an internal error. Theoretically, the packet could continue through the stack (as it would have if no XDP program had been running), but XDP uses "fail-close" semantics. Edits to the packet are carried through all XDP paths. Note that everything up through and including <tt>XDP_TX</tt> can be represented in two bits; this will be important later when passing flags to bpf helpers.

Think of <tt>XDP_ABORTED</tt> as returning -1 from the eBPF program; it's meant to indicate an internal error. Theoretically, the packet could continue through the stack (as it would have if no XDP program had been running, or <tt>XDP_PASS</tt> was returned), but XDP uses "fail-close" semantics. Edits to the packet are carried through all XDP paths. Note that everything up through and including <tt>XDP_TX</tt> can be represented in two bits; this will be important later when passing flags to bpf helpers.

<tt>xdp-loader status</tt> will list NICs and show details regarding any attached XDP programs. <tt>ethtool -S</tt> shows XDP statistics. <tt>ip link</tt> will also show a summary of devices' XDP chains. <tt>xdp_dispatcher</tt> is a metaprogram loaded by <tt>xdp-loader</tt> to support chaining multiple XDP programs; it will be present whenever programs were loaded using <tt>xdp-loader</tt>.

@@ Line 28: / Line 28: @@
 * <tt>XDP_TX</tt>: emit the packet back out the interface on which it was received
 * <tt>XDP_REDIRECT</tt>: send the packet to another NIC or an <tt>AF_XDP</tt> socket
-Think of <tt>XDP_ABORTED</tt> as returning -1 from the eBPF program; it's meant to indicate an internal error. Theoretically, the packet could continue through the stack (as it would have if no XDP program had been running), but XDP uses "fail-close" semantics. Edits to the packet are carried through all XDP paths. Note that everything up through and including <tt>XDP_TX</tt> can be represented in two bits; this will be important later when passing flags to bpf helpers.
+Think of <tt>XDP_ABORTED</tt> as returning -1 from the eBPF program; it's meant to indicate an internal error. Theoretically, the packet could continue through the stack (as it would have if no XDP program had been running, or <tt>XDP_PASS</tt> was returned), but XDP uses "fail-close" semantics. Edits to the packet are carried through all XDP paths. Note that everything up through and including <tt>XDP_TX</tt> can be represented in two bits; this will be important later when passing flags to bpf helpers.
 <tt>xdp-loader status</tt> will list NICs and show details regarding any attached XDP programs. <tt>ethtool -S</tt> shows XDP statistics. <tt>ip link</tt> will also show a summary of devices' XDP chains. <tt>xdp_dispatcher</tt> is a metaprogram loaded by <tt>xdp-loader</tt> to support chaining multiple XDP programs; it will be present whenever programs were loaded using <tt>xdp-loader</tt>.

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