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bpf.2: Minor tweaks after comments from Daniel Borkmann 

Reported-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Michael Kerrisk 2015-08-07 11:39:07 +02:00
parent 57f8da4c64
commit aabe0499f3
1 changed files with 9 additions and 6 deletions
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15
man2/bpf.2
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@ -67,8 +67,9 @@ This type of map stores file descriptors referring to other eBPF programs.
When a lookup in the map is performed, the program flow is
redirected in-place to the beginning of another eBPF program and does not
return back to the calling program.
The level of nesting has a fixed limit of 32, so that infinite loops cannot
be crafted.
The level of nesting has a fixed limit of 32,
.\" Defined by the kernel constant MAX_TAIL_CALL_CNT in include/linux/bpf.h
so that infinite loops cannot be crafted.
At runtime, the program file descriptors stored in the map can be modified,
so program functionality can be altered based on specific requirements.
All programs referred to in a program-array map must
@ -672,10 +673,12 @@ The invoked program will then reuse the same stack.
When a jump into the new program has been performed,
it won't return to the old program anymore.
If no eBPF program is found at the given index of the program array,
.\" FIXME The array does not contain eBPF programs, but rather file
.\" descriptors. So, what does "no eBPF program is found" here
.\" really mean?
If no eBPF program is found at the given index of the program array
(because the map slot doesn't contain a valid program file descriptor,
the specified lookup index/key is out of bounds,
or the limit of 32
.\" MAX_TAIL_CALL_CNT
nested calls has been exceed),
execution continues with the current eBPF program.
This can be used as a fall-through for default cases.