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The test_lwt_bpf is a script that tests the functionality of BPF through
the output of the ftrace with bpf_trace_printk. Currently, this program
is not operating normally for several reasons.
First of all, this test script can't parse the ftrace results properly.
GNU sed tries to be as greedy as possible when attempting pattern
matching. Due to this, cutting metadata (such as timestamp) from the
log entry of ftrace doesn't work properly, and also desired log isn't
extracted properly. To make sed stripping clearer, 'nocontext-info'
option with the ftrace has been used to remove metadata from the log.
Also, instead of using unclear pattern matching, this commit specifies
an explicit parse pattern.
Also, unlike before when this test was introduced, the way
bpf_trace_printk behaves has changed[1]. The previous bpf_trace_printk
had to always have '\n' in order to print newline, but now that the
bpf_trace_printk call includes newline by default, so '\n' is no longer
needed.
Lastly with the lwt ENCAP_BPF out, the context information with the
sk_buff protocol is preserved. Therefore, this commit changes the
previous test result from 'protocol 0' to 'protocol 8', which means
ETH_P_IP.
[1]: commit ac5a72ea5c ("bpf: Use dedicated bpf_trace_printk event instead of trace_printk()")
Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
Link: https://lore.kernel.org/r/20230115071613.125791-4-danieltimlee@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
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.