1xdpdump(a8)simple tcpdump like tool for capturing packets at the XDP laxydeprdump(8)
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6 xdpdump - a simple tcpdump like tool for capturing packets at the XDP
7 layer
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10 xdpdump is a simple XDP packet capture tool that tries to behave simi‐
11 lar to tcpdump, however, it has no packet filter or decode capabili‐
12 ties.
13 This can be used for debugging XDP programs that are already loaded on
16 an interface. Packets can be dumped/inspected before on entry to XDP
17 program, or after at exit from an XDP program. Furthermore, at exit
18 the XDP action is also captured. This means that even packets that are
19 dropped at the XDP layer can be captured via this tool.
20 xdpdump works by attaching a bpf trace program to the XDP entry and/or
23 exit function which stores the raw packet in a perf trace buffer. If no
24 XDP program is loaded this approach can not be used and the tool will
25 use a libpcap live-capture to be backward compatible.
26 Running xdpdump
29 The syntax for running xdpdump is:
30 Usage: xdpdump [options]
32 XDPDump tool to dump network traffic
34 Options:
36 --rx-capture <mode> Capture point for the rx direction (valid values: entry,exit)
37 -D, --list-interfaces Print the list of available interfaces
38 -i, --interface <ifname> Name of interface to capture on
39 --perf-wakeup <events> Wake up xdpdump every <events> packets
40 -p, --program-names <prog> Specific program to attach to
41 -s, --snapshot-length <snaplen> Minimum bytes of packet to capture
42 --use-pcap Use legacy pcap format for XDP traces
43 -w, --write <file> Write raw packets to pcap file
44 -x, --hex Print the full packet in hex
45 -v, --verbose Enable verbose logging (-vv: more verbose)
46 --version Display version information
47 -h, --help Show this help
48
51 The xdpdump tool tries to mimic the basic tcpdump options, but just in
52 case below each of the available options is explained:
53 --rx-capture <mode>
56 Specify where the ingress packet gets captured. Either at the entry of
57 the XDP program and/or exit of the XDP program. Valid options are en‐
58 try, exit, or both entry,exit. The packet at exit can be modified by
59 the XDP program. If you are interested to see both the original and
60 modified packet, use the entry,exit option. With this, each packet is
61 captured twice. The default value for this is entry.
62 -D, --list-interfaces
64 Display a list of available interfaces and any XDP program loaded
65 --load-xdp-mode
67 Specifies which loader mode to use with the --load-xdp-program option.
68 The valid values are ‘native’, which is the default in-driver XDP mode,
69 ‘skb’, which causes the so-called skb mode (also known as generic XDP)
70 to be used, ‘hw’ which causes the program to be offloaded to the hard‐
71 ware, or ‘unspecified’ which leaves it up to the kernel to pick a mode
72 (which it will do by picking native mode if the driver supports it, or
73 generic mode otherwise). Note that using ‘unspecified’ can make it dif‐
74 ficult to predict what mode a program will end up being loaded in. For
75 this reason, the default is ‘native’.
76 --load-xdp-program
78 If no XDP program is loaded on the interface, by default, xdpdump will
79 fallback to libpcap's live capture mode to capture the packets. Alter‐
80 natively, with this option, you can ask xdpdump to load an XDP program
81 to capture the packets directly.
82 -i, --interface <ifname>
84 Listen on interface ifname. Note that if no XDP program is loaded on
85 the interface it will use libpcap's live capture mode to capture the
86 packets.
87 --perf-wakeup <events>
89 Let the Kernel wake up xdpdump once for every <events> being posted in
90 the perf ring buffer. The higher the number the less the impact is on
91 the actual XDP program. The default value is 0, which automatically
92 calculates the value based on the available CPUs/buffers. Use -v to see
93 the actual used value.
94 -p, --program-names [<prog>|all]
96 This option allows you to capture packets for a specific, set of, or
97 all XDP programs loaded on the interface. You can either specify the
98 actual program names or program IDs separated by commas. In the case
99 where multiple programs are attached with the same name, you should use
100 the program ID. Use the -D option to see the loaded programs and their
101 IDs.
102 In addition, the Linux API does not provide the full name of the at‐
106 tached eBPF entry function if it's longer than 15 characters. xdpdump
107 will try to guess the correct function name from the available BTF de‐
108 bug information. However, if multiple functions exist with the same
109 leading name, it can not pick the correct one. It will dump the avail‐
110 able functions, and you can choose the correct one, and supply it with
111 this option. If you have programs with duplicate long names, you also
112 need to specify the program ID with the full name. This can be done by
113 adding the id to the name with the @<id> suffix.
114 -P, --promiscuous-mode
116 This option puts the interface into promiscuous mode.
117 -s, --snapshot-length <snaplen>
119 Capture snaplen bytes of a packet rather than the default 262144 bytes.
120 --use-pcap
122 Use legacy pcap format for XDP traces. By default, it will use the
123 PcapNG format so that it can store various metadata.
124 -w, --write <file>
126 Write the raw packets to a pcap file rather than printing them out
127 hexadecimal. Standard output is used if file is -.
128 -x, --hex
130 When dumping packets on the console also print the full packet content
131 in hex.
132 -v, --verbose
134 Enable debug logging. Specify twice for even more verbosity.
135 --version
137 Display xpdump version information and exit.
138 -h, --help
140 Display a summary of the available options
141
144 The below will load the xdp-filter program on eth0, but it does not do
145 any actual filtering:
146 # xdp-filter load --mode skb eth0
148 #
149 # xdpdump -D
150 Interface Prio Program name Mode ID Tag Chain actions
151 --------------------------------------------------------------------------------------
152 lo <No XDP program loaded!>
153 eth0 xdp_dispatcher skb 10651 d51e469e988d81da
154 => 10 xdpfilt_alw_all 10669 0b394f43ab24501c XDP_PASS
155 Now we can try xdpdump:
158 # xdpdump -i eth0 -x
160 listening on eth0, ingress XDP program ID 10651 func xdp_dispatcher, capture mode entry, capture size 262144 bytes
161 1584373839.460733895: xdp_dispatcher()@entry: packet size 102 bytes, captured 102 bytes on if_index 2, rx queue 0, id 1
162 0x0000: 52 54 00 db 44 b6 52 54 00 34 38 da 08 00 45 48 RT..D.RT.48...EH
163 0x0010: 00 58 d7 dd 40 00 40 06 ec c3 c0 a8 7a 01 c0 a8 .X..@.@.....z...
164 0x0020: 7a 64 9c de 00 16 0d d5 c6 bc 46 c9 bb 11 80 18 zd........F.....
165 0x0030: 01 f5 7b b4 00 00 01 01 08 0a 77 0a 8c b8 40 12 ..{.......w...@.
166 0x0040: cc a6 00 00 00 10 54 ce 6e 20 c3 e7 da 6c 08 42 ......T.n ...l.B
167 0x0050: d6 d9 ee 42 42 f0 82 c9 4f 12 ed 7b 19 ab 22 0d ...BB...O..{..".
168 0x0060: 09 29 a9 ee df 89 .)....
169 1584373839.462340808: xdp_dispatcher()@entry: packet size 66 bytes, captured 66 bytes on if_index 2, rx queue 0, id 2
171 0x0000: 52 54 00 db 44 b6 52 54 00 34 38 da 08 00 45 48 RT..D.RT.48...EH
172 0x0010: 00 34 d7 de 40 00 40 06 ec e6 c0 a8 7a 01 c0 a8 .4..@.@.....z...
173 0x0020: 7a 64 9c de 00 16 0d d5 c6 e0 46 c9 bc 85 80 10 zd........F.....
174 0x0030: 01 f5 74 0c 00 00 01 01 08 0a 77 0a 8c ba 40 12 ..t.......w...@.
175 0x0040: d2 34 .4
176 ^C
177 2 packets captured
178 0 packets dropped by perf ring
179 Below are two more examples redirecting the capture file to tcpdump or
182 tshark:
183 # xdpdump -i eth0 -w - | tcpdump -r - -n
185 listening on eth0, ingress XDP program ID 10651 func xdp_dispatcher, capture mode entry, capture size 262144 bytes
186 reading from file -, link-type EN10MB (Ethernet)
187 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
188 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
189 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
190 # xdpdump -i eth0 -w - | tshark -r - -n
192 listening on eth0, ingress XDP program ID 10651 func xdp_dispatcher, capture mode entry, capture size 262144 bytes
193 1 0.000000 192.168.122.1 → 192.168.122.100 SSH 102 Client: Encrypted packet (len=36)
194 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
195 3 12.218164 192.168.122.1 → 192.168.122.100 SSH 102 Client: Encrypted packet (len=36)
196 One final example capturing specific XDP programs loaded on the inter‐
199 face:
200 # xdpdump -D
202 Interface Prio Program name Mode ID Tag Chain actions
203 --------------------------------------------------------------------------------------
204 lo <No XDP program loaded!>
205 eth0 xdp_dispatcher skb 10558 d51e469e988d81da
206 => 5 xdp_test_prog_w 10576 b5a46c6e9935298c XDP_PASS
207 => 10 xdp_pass 10582 3b185187f1855c4c XDP_PASS
208 => 10 xdp_pass 10587 3b185187f1855c4c XDP_PASS
209 We would like to see the packets on the xdp_dispatcher() and the 2nd
212 xdp_pass() program:
213 # xdpdump -i eth0 --rx-capture=entry,exit -p xdp_dispatcher,xdp_pass@10587
215 or
216 # xdpdump -i eth0 --rx-capture=entry,exit -p 10558,10587
217 listening on eth0, ingress XDP program ID 10558 func xdp_dispatcher, ID 10587 func xdp_pass, capture mode entry/exit, capture size 262144 bytes
218 1607694215.501287259: xdp_dispatcher()@entry: packet size 102 bytes on if_index 2, rx queue 0, id 1
219 1607694215.501371504: xdp_pass()@entry: packet size 102 bytes on if_index 2, rx queue 0, id 1
220 1607694215.501383099: xdp_pass()@exit[PASS]: packet size 102 bytes on if_index 2, rx queue 0, id 1
221 1607694215.501394709: xdp_dispatcher()@exit[PASS]: packet size 102 bytes on if_index 2, rx queue 0, id 1
222 ^C
223 4 packets captured
224 0 packets dropped by perf ring
225
228 Please report any bugs on Github: https://github.com/xdp-project/xdp-
229 tools/issues
230
233 xdpdump was written by Eelco Chaudron
234V1.2.6 AUGUST 16, 2022 xdpdump(8)