i used cat /proc/pid/net/udp6 and become:
sl local_address remote_address st tx_queue rx_queue tr tm->when retrnsmt uid timeout inode ref pointer drops
63: 00000000000000000000000000000000:D9BF 00000000000000000000000000000000:0000 07 00000000:00000000 00:00000000 00000000 1000 0 181584 2 c16e8d00 0
I know how its structured and the 00000000000000000000000000000000:D9BFmust be local ip. How can I convert it to normal ip format like 127.0.0.1?
InetAddress a = InetAddress.getByAddress(DatatypeConverter.parseHexBinary("0A064156"));
Related
I use tcpdump to catch some tcp packets, when analyzing them according to ip/tcp packet schema, the packet seems to be broken. Here is a sample packet I got from tcpdump output. Is any one familiar with them?
Should not the first 4 bit of ip packet always be 0100 in under ipv4?
ip packet: https://en.wikipedia.org/wiki/IPv4
some examples: http://mike.passwall.com/networking/samplepacket.html
13:11:43.330397 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 60)
172.16.0.14.16668 > 36.24.146.114.64853: Flags [S.], cksum 0xdc0f (correct), seq 3029391223, ack 129060479, win 14480, options [mss 1460,sackOK,TS val 1254469916 ecr 1492278057,nop,wscale 6], length 0
0x0000: feee 809f 3247 5254 0054 aa9f 0800 4500 ....2GRT.T....E.
0x0010: 003c 0000 4000 4006 d813 ac10 000e 2418 .<..#.#.......$.
0x0020: 9272 411c fd55 b490 d777 07b1 4e7f a012 .rA..U...w..N...
0x0030: 3890 dc0f 0000 0204 05b4 0402 080a 4ac5 8.............J.
uname -a
# Linux VM_0_14_centos 2.6.32-754.2.1.el6.x86_64 #1 SMP Fri Jul 13 12:50:12 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
# tcpdump
tcpdump tcp -vv -XX -n -i eth0 port 16668
0x0000: feee 809f 3247 5254 0054 aa9f 0800 4500 ....2GRT.T....E.
The first 14 bytes are from the link layer (EN10MB). The IP layer only starts with 4500, where the 4 (binary 0100) are the first 4 bits which describe the version number, i.e. IP version 4.
These link layer data are explicitly requested by the -XX option which is used by the OP as pointed out in a comment by David Hoelzer. To cite from the documentation of tcpdump:
-XX When parsing and printing, in addition to printing the headers of each packet, print the data of each packet, including its link level header, in hex and ASCII.
i'm trying to subset a large dataframe by date field ad facing strange behaviour:
1) find interesting time interval:
> ld[ld$bps>30000000,]
Date.first.seen Duration Proto Src.IP.Addr Src.Pt Dst.IP.Addr Dst.Pt Tos Packets Bytes bps
1400199 2015-03-31 13:52:24 0.008 TCP 3.3.3.3 3128 4.4.4.4 65115 0 39 32507 32500000
1711899 2015-03-31 14:58:10 0.004 TCP 3.3.3.3 3128 4.4.4.7 49357 0 29 23830 47700000
2) and try to look whats happening on that second:
> ld[ld$Date.first.seen=="2015-03-31 13:52:24",]
Date.first.seen Duration Proto Src.IP.Addr Src.Pt Dst.IP.Addr Dst.Pt Tos Packets Bytes bps
1401732 2015-03-31 13:52:24 17.436 TCP 3.3.3.3 3128 6.6.6.6 51527 0 3 1608 737
don't really understand the behavior - i should get way more results.
for example
> ld[1399074,]
Date.first.seen Duration Proto Src.IP.Addr Src.Pt Dst.IP.Addr Dst.Pt Tos Packets Bytes bps
1399074 2015-03-31 13:52:24 0.152 TCP 10.10.10.10 3128 11.11.11.11 62375 0 8 3910 205789
for date i use POSIXlt
> str(ld)
'data.frame': 2657583 obs. of 11 variables:
$ Date.first.seen: POSIXlt, format: "2015-03-31 06:00:00" "2015-03-31 06:00:00" "2015-03-31 06:00:00" "2015-03-31 06:00:01" ...
...
would appreciate any assistance. thanks!
POSIXlt may carry additional info which is supressed when printing the entire data.frame, timezone, daylight savings etc. Have a look at https://stat.ethz.ch/R-manual/R-devel/library/base/html/DateTimeClasses.html.
Printing only the POSIXlt variable (ld$Date.first.seen) does generally supply at least some of this additional information.
If you're not for some particular reason required to keep your variable in the POSIXlt and if you don't need the extra functionality the format enables, a simple:
ld$Date.first.seen = as.character(ld$Date.first.seen)
Added before your subset statement will probably solve your problem.
Trying to deconstruct this TCPdump BPF style filter, and need some help:
'tcp[((tcp[12:1] & 0xf0) >> 2):4] = 0x47455420'
Its taken from here
Steps that have taken to better understand what is going on:
1. Lets convert the 0x47455420 to ascii
===> GET
===> tcp[((tcp[12:1] & 0xf0) >> 2):4] = GET
2. Examine the inner tcp filter: (tcp[12:1] & 0xf0)
===> the 0xf0 == 0000 0000 1111 0000 ===> I suppose it is save to discard the upper zeros so I can write 1111 0000
===> tcp[12:1] == 08 (start filtering from byte 13 (0 based indexing, so you could also say start with the byte that has index 12) for 1 byte, so only 13th byte);
===> 08 == 0000 1000
===> 0000 1000 & 1111 0000 == 0000 (bitwise and = if both are 1 then end result is one)
This is where I got confused. The explanation in the hyperlink I provided above is saying
multiply it by four ( (tcp[12:1] & 0xf0)>>2 ) which should give the tcp header length
Impossible if it is zero. Please:
help me find the mistake in my calculations (maybe I'm mixing TCP and IP headers?);
provide some guidance whether my logic is correct.
This is the packet:
19:10:30.091065 IP (tos 0x0, ttl 63, id 40127, offset 0, flags [DF], proto TCP (6), length 2786)
10.240.35.81.47856 > 172.17.13.201.8080: Flags [P.], cksum 0xf2ef (incorrect -> 0xb8f8), seq 2263020471:2263023205, ack 4187927811, win 28, options [nop,nop,TS val 1906863883 ecr 214445688], length 2734
0x0000: 1a17 8e8a a3a0 026d 627d 049c 0800 4500 .......mb}....E.
0,1 2,3 ... ... ... ... 12,13 ... <=== byte indexes
1,2 3,4 ... ... ... ... 13,14 ... <=== counting how many bytes
0x0010: 0ae2 9cbf 4000 3f06 ac3b 0af0 2351 ac11 ....#.?..;..#Q.. <=== 0x0010 number correctly identifies that the first two diggits are the 16th byte
16,17 ... ...
0x0020: 0dc9 baf0 1f90 86e2 f3b7 f99e b503 8018 ................
0x0030: 001c f2ef 0000 0101 080a 71a8 6f0b 0cc8 ..........q.o...
0x0040: 2e78 4745 5420 2f69 636f 6e73 2f75 6e6b .xGET./icons/unk
0x0050: 6e6f 776e 2e67 6966 2048 5454 502f 312e nown.gif.HTTP/1.
0x0060: 310d 0a68 6f73 743a 2070 6870 2d6d 696e 1..host:.php-min
tcp[12:1] is the byte at an offset of 12 bytes from the beginning of the TCP header; the 12 is not the offset from the beginning of the packet, it's the offset from the beginning of the TCP header (it's tcp[12:1], not ether[12:1] or something such as that). The "1" is the number of bytes being referred to.
According to RFC 793, which is the specification for TCP, the byte at an offset of 12 bytes from the beginning of the TCP header contains the data offset in the upper 4 bits and the lower 4 bits are reserved bits. The data offset is "The number of 32 bit words in the TCP Header", which "indicates where the data begins".
The data in the packet is being displayed as a sequence of byte pairs. It's a bit easier to understand if presented as a sequence of individual bytes, so:
0x0000: 1a 17 8e 8a a3 a0 02 6d 62 7d 04 9c 08 00 45 00
eth dest eth src etype IP hdr
The first 6 bytes of the packet are the Ethernet destination address.
The next 6 bytes of the packet are the Ethernet source address.
The 2 bytes after that are the Ethernet type value; it's big-endian, so its value is 0x0800, which is the Ethernet type value for IPv4.
The next 2 bytes are the first 2 bytes of the IPv4 header. According to RFC 791, which is the specification for IPv4, the first byte of the IPv4 header contains the IP version in the upper 4 bits and the header length in the lower 4 bits. That byte has a value of 0x45, so the IP version is 4 (as it should be, for IPv4) and the header length is 5. The header length "is the length of the internet header in 32 bit words", so that's 5 32-bit words, or 20 bytes.
So, for now, let's skip the IPv4 header and go to the TCP header:
0x0020: 0d c9 ba f0 1f 90 86 e2 f3 b7 f9 9e b5 03 80 18
TCP header 12 13
So byte 12 of the TCP header is 0x80. 0x80 & 0xf0 is 0x80, and 0x80 >> 2 is 0x20, which is 32; this is consistent with the upper 4 bits of that byte being the data offset, in 32-bit words, as 8*4 = 32.
tcp[((tcp[12:1] & 0xf0) >> 2):4] is thus, for this packet, tcp[32:4], i.e. the 4 bytes at an offset of 32 from the beginning of the TCP header.
32 bytes from the beginning of the TCP header is:
0x0040: 2e78 4745 5420 2f69 636f 6e73 2f75 6e6b
^
there, and that's the "GET" header of the HTTP request, beginning at the beginning of the TCP segment data. Te 4 bytes in question are "GET ".
So the 12 in tcp[12:1] is not the offset from the beginning of the packet, it's the offset from the beginning of the TCP header (it's tcp[12:1], not ether[12:1] or something such as that).
And, in answer to the questions about the bytes of the packet and what they are:
0x0000: 1a 17 8e 8a a3 a0: Ethernet destination
02 6d 62 7d 04 9c: Ethernet source
08 00: Ethernet type/length field - 0x0800 = IPv4
So the first 14 (0x000e) bytes of the packet are the Ethernet header.
In this packet, the Ethernet type/length field is 0x0800, so the Ethernet payload, following the Ethernet header, is an IPv4 packet, beginning with an IPv4 header:
45: IPv4 version/header length
00: IPv4 Type of Service/Differentiated Service
0x0010: 0a e2: IPv4 total length
9c bf: IPv4 identification
40 00: IPv4 flags/fragment offset
3f: IPv4 time-to-live
06: IPv4 (next) protocol - 6 = TCP
ac 3b: IPv4 header checksum
0a f0 23 51: IPv4 source address
ac 11: first 2 bytes of IPv4 destination address
0x0020: 0d c9: second 2 bytes of IPv4 destination address
The IPv4 header length is 5, so the IPv4 header is 20 bytes. That's the minimum IPv4 header length; it can't be smaller, but it can be larger, if there are IPv4 options after the fixed-length part of the header. There aren't any, in this case.
As the protocol field has the value 6, the IPv4 payload is a TCP packet:
ba f0: TCP source port (47856)
1f 90: TCP destination port (8080)
86 e2 f3 b7: TCP sequence number
f9 9e b5 03: TCP acknowledgment number
80: TCP data offset + reserved bits
18: reserved bits + TCP flags
0x0030: 00 1c: TCP window
f2 ef: TCP checksum
00 00: TCP urgent pointer
That's the 20-byte fixed-length portion of the TCP header; however, the TCP header length is 32 bytes, so there are an additional 12 bytes of TCP options in the header:
01: TCP No-Operation option
01: TCP No-Operation option
08 0a 71 a8 6f 0b 0c c8: first 8 bytes of TCP Timestamp option
0x0040: 2e 78: last 2 bytes of TCP Timestamp option
A TCP header's length must be a multiple of 32 bits, i.e. a multiple of 4 bytes; TCP options might not be a multiple of 4 in length - the TCP Timestamp option is 10 bytes long - so the No-Operation option is used for padding.
So those 32 bytes were the TCP header; what follows is the TCP payload. Apparently, this is on an HTTP connection (the packet is being sent to port 8080, which is an alternate HTTP port), and this is the beginning of an HTTP GET request:
47 45 54 20 2f 69 63 6f 6e 73 2f 75 6e 6b
0x0050: 6e 6f 77 6e 2e 67 69 66 20 48 54 54 50 2f 31 2e
0x0060: 31 0d 0a 68 6f 73 74 3a 20 70 68 70 2d 6d 69 6e
So:
as this was captured either on an Ethernet or on a Wi-Fi network when not in monitor mode (or on some other type of network that either uses Ethernet headers or on which the adapter or driver supplies "fake Ethernet" headers, as with Wi-Fi), the packet will start with an Ethernet header;
as the Ethernet type value is 0x0800, it's followed by an IPv4 header;
as the IPv4 protocol value is 6, it's followed by a TCP header;
as one of the TCP port numbers is a port number typically used by HTTP (8080), it's probably followed by HTTP data of some sort (this isn't guaranteed, however - TCP port numbers are more like hints).
For ARP over the same network, you'll again have an Ethernet header (the ffff ffff is the Ethernet broadcast address, so the packet is being broadcast, as ARP requests usually are), with an Ethernet type of 0x0806, which is the Ethernet type value for ARP.
For ICMP over the same network, you'll again have an Ethernet header, and you'll also have an IPv4 header, so the Ethernet type will be 0x0800. The value in the protocol field in the IPv4 header will be 1, for ICMP.
I'm trying to discover devices, from a coordinator, in my network.
So I sent an ND command to the coordinator and I'm correctly receiving response from other Xbee.
The next step will be to store the information I've received in a web application, in oder to send commands and data.
However, what I'm still missing is some parts in the frame respose. So far I've mapped the frame like this:
1 7E start frame
===== =================== MESSAGE LENGHT
2-3 0x00 0x19 -> 25
===== =================== PACKET TYPE
4 88 -> response to a remote AT command
5 02 frame ID
===== =================== AT COMMAND
6-7 0x4E 0x44 "ND"
8 00 status byte (00 -> OK)
===== =================== MY - Remote Address
9-10 0x17 0x85
===== =================== SH - SERIAL NUMBER HIGH
11-14 0x00 0x13 0xA2 0x00
===== =================== SL - SERIAL NUMBER LOW
15-18 0x40 0xB4 0x50 0x23
===== =================== SIGNAL
19 20
= ======== NI - Node Identifier
20 00
21 FF
22 FE
23 01
24 00
25 C1
26 05
27 10
28 1E
===== ===== CHECKSUM (25th bytes from MESSAGE LENGHT)
29 19
So, where I can find in this response the address of the device ?
My guess is in the NI part of the message but, I haven't find any example/information of how the data are organised.
Could someone point me in the right direction?
As someone told me in the dig.com forum
NI<CR> (Variable length)
PARENT_NETWORK ADDRESS (2 Bytes)<CR>
DEVICE_TYPE (1 Byte: 0=Coord, 1=Router, 2=End Device)
STATUS (1 Byte: Reserved)
PROFILE_ID (2 Bytes)
MANUFACTURER_ID (2 Bytes
So, loking to my frame response:
00 --- Node Identifier variable, (here 1 byte = 00 because no value is set up).
FFFE --- parent network address (2 bytes)
01 --- device type
00 --- status
C105 --- profile id
101E --- manufacturing id
This, afaik, means that in this last part of the frame, no information about address of the device are given. Only information are the SL and SH.
The 16-bit network address is what you've labeled "MY" (0x1785), and the 64-bit MAC address is the combination of SH/SL (00 13 A2 00 40 B4 50 23).
I've checked the tcpdump man page and thought I understood the example provided there. But the one that I am getting is something I'm not able to understand completely.
ORIGINAL: Simulator Output
LINE 1: 20:01:13.442111 IP 10.0.0.1.12345 > 10.0.0.2.54321: S 1234:1234(0) win 65535
LINE 2: 20:01:13.471705 IP 10.0.0.2.54321 > 10.0.0.1.12345: S 4321:4321(0) ack 1235 win 65535
LINE 3: 20:01:13.497389 IP 10.0.0.1.14640 > 10.0.0.2.12756: . ack 4322 win 65535
LINE 4: 20:01:13.497422 IP 10.0.0.1.12345 > 10.0.0.2.54321: . 1235:2682(1447) win 65535
LINE 5: 20:01:14.023273 IP 10.0.0.2.12756 > 10.0.0.1.14640: . ack 5768 win 65535
This is what I understand:
LINE 1: 1 sends 2 0 bytes starting with SEQ number 1234
LINE 2: 2 sends 1 0 bytes starting with SEQ number 4321 and an ACK = (1's SEQ + 1) i.e. 1235
LINE 3: 1 sends 2 0 bytes with an ACK = (2's SEQ + 1) i.e. 4322
LINE 4: 1 sends 2 1447 bytes starting with SEQ number 1235 until 2682 (1447 bytes in total)
LINE 5: 2 sends 1 0 bytes with an ACK = 5768? What is this number? Isn't it supposed to be 2683?
Maybe I am missing something too obvious. Can someone point it out please?
EDIT 1: Simulator output (grepped one connection info)
20:01:13.442111 IP 10.0.0.1.12345 > 10.0.0.2.54321: S 1234:1234(0) win 65535
20:01:13.471705 IP 10.0.0.2.54321 > 10.0.0.1.12345: S 4321:4321(0) ack 1235 win 65535
20:01:13.497422 IP 10.0.0.1.12345 > 10.0.0.2.54321: . 1235:2682(1447) win 65535
20:01:14.573322 IP 10.0.0.2.54321 > 10.0.0.1.12345: . ack 5981 win 65535
20:01:14.593870 IP 10.0.0.1.12345 > 10.0.0.2.54321: . 4129:5576(1447) win 65535
20:01:14.639457 IP 10.0.0.1.12345 > 10.0.0.2.54321: . 7023:8470(1447) win 65535
20:01:14.639606 IP 10.0.0.1.12345 > 10.0.0.2.54321: . 9917:10640(723) win 65535
20:01:14.660971 IP 10.0.0.2.54321 > 10.0.0.1.12345: . ack 11769 win 65535
20:01:14.693847 IP 10.0.0.1.12345 > 10.0.0.2.54321: . 12087:13534(1447) win 65535
20:01:14.726564 IP 10.0.0.2.54321 > 10.0.0.1.12345: . ack 15964 win 65535
Question: The ACK still seems to be different. It is 5981 instead of 2683.
EDIT 2: Real TCP output
22:20:14.492625 IP 72.14.204.99.80 > 10.0.2.15.59745: S 255616001:255616001(0) ack 1727704513 win 65535 <mss 1460>
22:20:14.495606 IP 10.0.2.15.59745 > 72.14.204.99.80: . ack 255616002 win 5840
22:20:14.501015 IP 10.0.2.15.59745 > 72.14.204.99.80: P 1727704513:1727705327(814) ack 255616002 win 5840
22:20:14.501746 IP 72.14.204.99.80 > 10.0.2.15.59745: . ack 1727705327 win 65535
22:20:14.562197 IP 72.14.204.99.80 > 10.0.2.15.59745: P 255616002:255616102(100) ack 1727705327 win 65535
22:20:14.562298 IP 10.0.2.15.59745 > 72.14.204.99.80: . ack 255616102 win 5840
22:20:14.630749 IP 10.0.2.15.59745 > 72.14.204.99.80: P 1727705327:1727706096(769) ack 255616102 win 5840
22:20:14.631228 IP 72.14.204.99.80 > 10.0.2.15.59745: . ack 1727706096 win 65535
22:20:14.692324 IP 72.14.204.99.80 > 10.0.2.15.59745: P 255616102:255616338(236) ack 1727706096 win 65535
22:20:14.692361 IP 10.0.2.15.59745 > 72.14.204.99.80: . ack 255616338 win 6432
Question: I tried as per your suggestion and grep'ed one connection's output. But this time, why is the ACK the way it is instead of SEQ+1?
check from the port number, It seems that LINE1, LINE2 and LINE5 belong to one session while LINE2 and LINE4 is in another session.
Instead using tcpdump for packet analysis, I highly suggest you to capture packets with tcpdump, and analyze the result with wireshark tool.
EDIT：
For the simulator stream, it mess up. Since the 10.0.0.1 -> 10.0.0.2's packets's sequence numbers is not completely, so I think maybe there some packet did not be captured and the timing is not show the real status. so you can ignore it.
For the real stream, it is okay. For syn packet, ack reply = seq +1; for content sending, ack = seq + len. The stream actually show this to us.