Add simple usage examples to man pages about xdp-tools

[chaudron]

xdp-dump already has some examples, or are you thinking of a missing example?

Examples
       The below will load the xdp-filter program on eth0, but it does not do any actual filtering:

              # xdp-filter load --mode skb eth0
              #
              # xdpdump -D
              if_index  if_name           XDP program entry function
              --------  ----------------  --------------------------------------------------
              1         lo                <No XDP program loaded!>
              2         eth0              xdpfilt_blk_all()

       Now we can try xdpdump:

              # xdpdump -i eth0
              1584373839.460733895: packet size 102 bytes, captured 102 bytes on if_index 2, rx queue 0, @entry
                0x0000:  52 54 00 db 44 b6 52 54 00 34 38 da 08 00 45 48  RT..D.RT.48...EH
                0x0010:  00 58 d7 dd 40 00 40 06 ec c3 c0 a8 7a 01 c0 a8  .X..@[email protected]...
                0x0020:  7a 64 9c de 00 16 0d d5 c6 bc 46 c9 bb 11 80 18  zd........F.....
                0x0030:  01 f5 7b b4 00 00 01 01 08 0a 77 0a 8c b8 40 12  ..{.......w...@.
                0x0040:  cc a6 00 00 00 10 54 ce 6e 20 c3 e7 da 6c 08 42  ......T.n ...l.B
                0x0050:  d6 d9 ee 42 42 f0 82 c9 4f 12 ed 7b 19 ab 22 0d  ...BB...O..{..".
                0x0060:  09 29 a9 ee df 89                                .)....

              1584373839.462340808: packet size 66 bytes, captured 66 bytes on if_index 2, rx queue 0, @entry
                0x0000:  52 54 00 db 44 b6 52 54 00 34 38 da 08 00 45 48  RT..D.RT.48...EH
                0x0010:  00 34 d7 de 40 00 40 06 ec e6 c0 a8 7a 01 c0 a8  .4..@[email protected]...
                0x0020:  7a 64 9c de 00 16 0d d5 c6 e0 46 c9 bc 85 80 10  zd........F.....
                0x0030:  01 f5 74 0c 00 00 01 01 08 0a 77 0a 8c ba 40 12  ..t.......w...@.
                0x0040:  d2 34                                            .4
              ^C
              2 packets captured
              0 packets dropped by perf ring

       Below are two more examples redirecting the capture file to tcpdump or tshark:

              # xdpdump -i eth0 -w - | tcpdump -r - -n
              reading from file -, link-type EN10MB (Ethernet)
              15:55:09.075887 IP 192.168.122.1.40928 > 192.168.122.100.ssh: Flags [P.], seq 3857553815:3857553851, ack 3306438882, win 501, options [nop,nop,TS val 1997449167 ecr 1075234328], length 36
              15:55:09.077756 IP 192.168.122.1.40928 > 192.168.122.100.ssh: Flags [.], ack 37, win 501, options [nop,nop,TS val 1997449169 ecr 1075244363], length 0
              15:55:09.750230 IP 192.168.122.1.40928 > 192.168.122.100.ssh: Flags [P.], seq 36:72, ack 37, win 501, options [nop,nop,TS val 1997449842 ecr 1075244363], length 36

              # xdpdump -i eth0 -w - | tshark -r - -n
                  1   0.000000 192.168.122.1 → 192.168.122.100 SSH 102 Client: Encrypted packet (len=36)
                  2   0.000646 192.168.122.1 → 192.168.122.100 TCP 66 40158 → 22 [ACK] Seq=37 Ack=37 Win=1467 Len=0 TSval=1997621571 TSecr=1075416765
                  3  12.218164 192.168.122.1 → 192.168.122.100 SSH 102 Client: Encrypted packet (len=36)

[tohojo]

Didn't have anything particular in mind. This came out of the last XDP meeting where I promised the docs people that we would have examples of usage for each tool in the man pages for them to work from. I just opened this issue so we wouldn't forget - if you think the xdpdump examples are sufficient as-is that is fine :)

[chaudron]

Didn't have anything particular in mind. This came out of the last XDP meeting where I promised the docs people that we would have examples of usage for each tool in the man pages for them to work from. I just opened this issue so we wouldn't forget - if you think the xdpdump examples are sufficient as-is that is fine :)

Ack, ok will remove me from the assignment list for now!!