=head1 NAME Ethereal - Interactively browse network traffic =head1 SYNOPSYS B S<[ B<-B> byte view height ]> S<[ B<-c> count ]> S<[ B<-f> filter expression ]> S<[ B<-h> ]> S<[ B<-i> interface ]> S<[ B<-k> ]> S<[ B<-m> font ]> S<[ B<-n> ]> S<[ B<-o> preference setting ] ...> S<[ B<-p> ]> S<[ B<-P> packet list height ]> S<[ B<-Q> ]> S<[ B<-r> infile ]> S<[ B<-R> filter expression ]> S<[ B<-S> ]> S<[ B<-s> snaplen ]> S<[ B<-T> tree view height ]> S<[ B<-t> time stamp format ]> S<[ B<-v> ]> S<[ B<-w> savefile]> =head1 DESCRIPTION B is a GUI network protocol analyzer. It lets you interactively browse packet data from a live network or from a previously saved capture file. B knows how to read B capture files, including those of B. In addition, B can read capture files from B (including B) and B, B, B (compressed or uncompressed), Microsoft B, AIX's B, B, B, B's WAN/LAN analyzer, B router debug output, HP-UX's B, the dump output from B ISDN routers, the output from B from the ISDN4BSD project, the output in B format from the Cisco Secure Intrusion Detection System, and B (pppdump format). There is no need to tell B what type of file you are reading; it will determine the file type by itself. B is also capable of reading any of these file formats if they are compressed using gzip. B recognizes this directly from the file; the '.gz' extension is not required for this purpose. Like other protocol analyzers, B's main window shows 3 views of a packet. It shows a summary line, briefly describing what the packet is. A protocol tree is shown, allowing you to drill down to exact protocol or field that you interested in. Finally, a hex dump shows you exactly what the packet looks like when it goes over the wire. In addition, B has some features that make it unique. It can assemble all the packets in a TCP conversation and show you the ASCII (or EBCDIC, or hex) data in that conversation. Display filters in B are very powerful; more fields are filterable in B than in other protocol analyzers, and the syntax you can use to create your filters is richer. As B progresses, expect more and more protocol fields to be allowed in display filters. Packet capturing is performed with the pcap library. The capture filter syntax follows the rules of the pcap library. This syntax is different from the display filter syntax. Compressed file support uses (and therefore requires) the zlib library. If the zlib library is not present, B will compile, but will be unable to read compressed files. =head1 OPTIONS =over 4 =item -B Sets the initial height of the byte view (bottom) pane. =item -c Sets the default number of packets to read when capturing live data. =item -f Sets the capture filter expression. =item -h Prints the version and options and exits. =item -i Sets the name of the network interface or pipe to use for live packet capture. Network interface names should match one of the names listed in "B" or "B". Pipe names should be either the name of a FIFO (named pipe) or ``-'' to read data from the standard input. Data read from pipes must be in libpcap format. =item -k Starts the capture session immediately. If the B<-i> flag was specified, the capture uses the specified interface. Otherwise, B searches the list of interfaces, choosing the first non-loopback interface if there are any non-loopback interfaces, and choosing the first loopback interface if there are no non-loopback interfaces; if there are no interfaces, B reports an error and doesn't start the capture. =item -m Sets the name of the font used by B for most text. B will construct the name of the bold font used for the data in the byte view pane that corresponds to the field selected in the protocol tree pane from the name of the main text font. =item -n Disables network object name resolution (such as hostname, TCP and UDP port names). =item -o Sets a preference value, overriding the default value and any value read from a preference file. The argument to the flag is a string of the form IB<:>I, where I is the name of the preference (which is the same name that would appear in the preference file), and I is the value to which it should be set. =item -p I put the interface into promiscuous mode. Note that the interface might be in promiscuous mode for some other reason; hence, B<-p> cannot be used to ensure that the only traffic that is captured is traffic sent to or from the machine on which B is running, broadcast traffic, and multicast traffic to addresses received by that machine. =item -P Sets the initial height of the packet list (top) pane. =item -Q Causes B to exit after the end of capture session (useful in batch mode with B<-c> option for instance); this option requires the B<-i> and B<-w> parameters. =item -r Reads packet data from I. =item -R When reading a capture file specified with the B<-r> flag, causes the specified filter (which uses the syntax of display filters, rather than that of capture filters) to be applied to all packets read from the capture file; packets not matching the filter are discarded. =item -S Specifies that the live packet capture will be performed in a separate process, and that the packet display will automatically be updated as packets are seen. =item -s Sets the default snapshot length to use when capturing live data. No more than I bytes of each network packet will be read into memory, or saved to disk. =item -T Sets the initial height of the tree view (middle) pane. =item -t Sets the format of the packet timestamp displayed in the packet list window. The format can be one of 'r' (relative), 'a' (absolute), or 'd' (delta). The relative time is the time elapsed between the first packet and the current packet. The absolute time is the actual date and time the packet was captured. The delta time is the time since the previous packet was captured. The default is relative. =item -v Prints the version and exits. =item -w Sets the default capture file name. =back =head1 INTERFACE =head2 MENU ITEMS =over 4 =item File:Open, File:Close, File:Reload Open, close, or reload a capture file. The I dialog box allows a filter to be specified; when the capture file is read, the filter is applied to all packets read from the file, and packets not matching the filter are discarded. =item File:Save, File:Save As Save the current capture, or the packets currently displayed from that capture, to a file. Check boxes let you select whether to save all packets, or just those that have passed the current display filter and/or those that are currently marked, and an option menu lets you select (from a list of file formats in which at particular capture, or the packets currently displayed from that capture, can be saved), a file format in which to save it. =item File:Print Prints, for all the packets in the current capture, either the summary line for the packet or the protocol tree view of the packet; when printing the protocol tree view, the hex dump of the packet can be printed as well. Printing options can be set with the I menu item, or in the dialog box popped up by this item. =item File:Print Packet Print a fully-expanded protocol tree view of the currently-selected packet. Printing options can be set with the I menu item. =item File:Quit Exits the application. =item Edit:Find Frame Allows you to search forward or backward, starting with the currently selected packet (or the most recently selected packet, if no packet is selected), for a packet matching a given display filter. =item Edit:Go To Frame Allows you to go to a particular numbered packet. =item Edit:Mark Frame Allows you to mark (or unmark if currently marked) the selected packet. =item Edit:Mark All Frames Allows you to mark all packets that are currently displayed. =item Edit:Unmark All Frames Allows you to unmark all packets that are currently displayed. =item Edit:Preferences Sets the packet printing, column display, TCP stream coloring, and GUI options (see L<"Preferences"> below). =item Edit:Filters Edits the saved list of filters, allowing filters to be added, changed, or deleted, and lets a selected filter be applied to the current capture, if any. =item Edit:Protocols Edits the list of protocols, allowing protocol dissection to be enabled or disabled. =item Capture:Start Initiates a live packet capture (see L<"Capture Preferences"> below). A temporary file will be created to hold the capture. The location of the file can be chosen by setting your TMPDIR environment variable before starting B. Otherwise, the default TMPDIR location is system-dependent, but is likely either F or F. =item Capture:Stop In a capture that updates the packet display as packets arrive (so that Ethereal responds to user input other than pressing the "Stop" button in the capture packet statistics dialog box), stops the capture. =item Display:Options Allows you to sets the format of the packet timestamp displayed in the packet list window to relative, absolute, or delta, to enable or disable the automatic scrolling of the packet list while a live capture is in progress or to enable or disable translation of addresses to names in the display. =item Display:Match Selected Creates and applies a display filter based on the data that is currently highlighted in the protocol tree. If that data is a field that can be tested in a display filter expression, the display filter will test that field; otherwise, the display filter will be based on absolute offset within the packet, and so could be unreliable if the packet contains protocols with variable-length headers, such as a source-routed token-ring packet. =item Display:Colorize Display Allows you to change the foreground and background colors of the packet information in the list of packets, based upon display filters. The list of display filters is applied to each packet sequentially. After the first display filter matches a packet, any additional display filters in the list are ignored. Therefore, if you are filtering on the existence of protocols, you should list the higher-level protocols first, and the lower-level protocols last. =item Display:Collapse All Collapses the protocol tree branches. =item Display:Expand All Expands all branches of the protocol tree. =item Display:Expand All Expands all branches of the protocol tree. =item Display:Show Packet In New Window Creates a new window containing a protocol tree view and a hex dump window of the currently selected packet; this window will continue to display that packet's protocol tree and data even if another packet is selected. =item Tools:Plugins Allows you to use and configure dynamically loadable modules (see L<"Plugins"> below). =item Tools:Follow TCP Stream If you have a TCP packet selected, it will display the contents of the data stream for the TCP connection to which that packet belongs, as text, in a separate window, and will leave the list of packets in a filtered state, with only those packets that are part of that TCP connection being displayed. You can revert to your old view by pressing ENTER in the display filter text box, thereby invoking your old display filter (or resetting it back to no display filter). The window in which the data stream is displayed lets you select whether to display: =over 4 =item whether to display the entire conversation, or one or the other side of it; =item whether the data being displayed is to be treated as ASCII or EBCDIC text or as raw hex data; =back =back =over 4 =item and lets you print what's currently being displayed, using the same print options that are used for the I menu item, or save it as text to a file. =back =head2 WINDOWS =over 4 =item Main Window The main window is split into three panes. You can resize each pane using a "thumb" at the right end of each divider line. Below the panes is a strip that shows the current filter and informational text. =over 6 =item Top Pane The top pane contains the list of network packets that you can scroll through and select. By default, the packet number, packet timestamp, source and destination addresses, protocol, and description are displayed for each packet; the I page in the dialog box popped up by I lets you change this (although, unfortunately, you currently have to save the preferences, and exit and restart Ethereal, for those changes to take effect). If you click on the heading for a column, the display will be sorted by that column; clicking on the heading again will reverse the sort order for that column. An effort is made to display information as high up the protocol stack as possible, e.g. IP addresses are displayed for IP packets, but the MAC layer address is displayed for unknown packet types. The right mouse button can be used to pop up a menu of operations. The middle mouse button can be used to mark a packet. =item Middle Pane The middle pane contains a I for the currently-selected packet. The tree displays each field and its value in each protocol header in the stack. The right mouse button can be used to pop up a menu of operations. =item Bottom Pane The lowest pane contains a hex dump of the actual packet data. Selecting a field in the I highlights the corresponding bytes in this section. The right mouse button can be used to pop up a menu of operations. =item Current Filter A display filter can be entered into the strip at the bottom. A filter for HTTP, HTTPS, and DNS traffic might look like this: tcp.port == 80 || tcp.port == 443 || tcp.port == 53 Selecting the I button lets you choose from a list of named filters that you can optionally save. Pressing the Return or Enter keys will cause the filter to be applied to the current list of packets. Selecting the I button clears the display filter so that all packets are displayed. =back =item Preferences The I dialog lets you control various personal preferences for the behavior of B. =over 6 =item Printing Preferences The radio buttons at the top of the I page allow you choose between printing packets with the I menu item as text or PostScript, and sending the output directly to a command or saving it to a file. The I text entry box is the command to send files to (usually B), and the I entry box lets you enter the name of the file you wish to save to. Additionally, you can select the I button to browse the file system for a particular save file. =item Column Preferences The I page lets you specify the number, title, and format of each column in the packet list. The I entry is used to specify the title of the column displayed at the top of the packet list. The type of data that the column displays can be specified using the I option menu. The row of buttons on the left perform the following actions: =over 6 =item New Adds a new column to the list. =item Change Modifies the currently selected list item. =item Delete Deletes the currently selected list item. =item Up / Down Moves the selected list item up or down one position. =item OK Currently has no effect. =item Save Saves the current column format as the default. =item Cancel Closes the dialog without making any changes. =back =item TCP Stream Preferences The I page can be used to change the color of the text displayed in the TCP stream window. To change a color, simply select an attribute from the "Set:" menu and use the color selector to get the desired color. The new text colors are displayed in a sample window. =item GUI Preferences The I page is used to modify small aspects of the GUI to your own personal taste: =over 6 =item Scrollbars The vertical scrollbars in the three panes can be set to be either on the left or the right. =item Selection Bars The selection bar in the packet list and protocol tree can have either a "browse" or "select" behavior. If the selection bar has a "browse" behavior, the arrow keys will move an outline of the selection bar, allowing you to browse the rest of the list or tree without changing the selection until you press the space bar. If the selection bar has a "select" behavior, the arrow keys will move the selection bar and change the selection to the new item in the packet list or protocol tree. The highlight method in the hex dump display for the selected protocol item can be set to use either inverse video, or bold characters. =item Fonts The "Font..." button lets you select the font to be used for most text. =item Colors The "Colors..." button lets you select the colors to be used for instance for the marked frames. =back =item Protocol Preferences There are also pages for various protocols that Ethereal dissects, controlling the way Ethereal handles those protocols. =back =item Filters The I dialog lets you create and modify filters, and set the default filter to use when capturing data or opening a capture file. The I entry specifies a descriptive name for a filter, e.g. B. The I entry is the text that actually describes the filtering action to take, as described above.The dialog buttons perform the following actions: =over 6 =item New If there is text in the two entry boxes, it creates a new associated list item. =item Change Modifies the currently selected list item to match what's in the entry boxes. =item Copy Makes a copy of the currently selected list item. =item Delete Deletes the currently selected list item. =item Apply Sets the currently selected list item as the active filter, and applies it to the current capture, if any. (The currently selected list item must be a display filter, not a capture filter.) If nothing is selected, turns filtering off. =item OK Sets the currently selected list item as the active filter. If nothing is selected, turns filtering off. =item Save Saves the current filter list in F<$HOME/.ethereal/filters>. =item Cancel Closes the dialog without making any changes. =back =item Capture Preferences The I dialog lets you specify various parameters for capturing live packet data. The I combo box lets you specify the interface from which to capture packet data, or the name of a FIFO from which to get the packet data. The I entry specifies the number of packets to capture. Entering 0 will capture packets indefinitely. The I entry lets you specify the capture filter using a tcpdump-style filter string as described above. The I entry specifies the file to save to, as in the I dialog above. You can specify the maximum number of bytes to capture per packet with the I entry, can specify whether the interface is to be put in promiscuous mode or not with the I check box, can specify that the display should be updated as packets are captured with the I check box, can specify whether in such a capture the packet list pane should scroll to show the most recently captured packets with the I check box, and can specify whether addresses should be translated to names in the display with the I check box. =item Display Options The I dialog lets you specify the format of the time stamp in the packet list. You can select "Time of day" for absolute time stamps, "Seconds since beginning of capture" for relative time stamps, or "Seconds since previous frame" for delta time stamps. You can also specify whether, when the display is updated as packets are captured, the list should automatically scroll to show the most recently captured packets or not and whether addresses should be translated to names in the display. =item Plugins The I dialog lets you view and configure the plugins available on your system. The I shows the name, description, version and state (enabled or not) of each plugin found on your system. The plugins are searched in the following directories: F, F and F<~/.ethereal/plugins> A plugin must be activated using the I button in order to use it to dissect packets. It can also be deactivated with the I button. The I button shows the filter used to select packets which should be dissected by a plugin (see L<"DISPLAY FILTER SYNTAX"> below). This filter can be modified. =head1 CAPTURE FILTER SYNTAX See manual page of tcpdump(8). =head1 DISPLAY FILTER SYNTAX Display filters help you remove the noise from a packet trace and let you see only the packets that interest you. If a packet meets the requirements expressed in your display filter, then it is displayed in the list of packets. Display filters let you compare the fields within a protocol against a specific value, compare fields against fields, and to check the existence of specified fields or protocols. The simplest display filter allows you to check for the existence of a protocol or field. If you want to see all packets which contain the IPX protocol, the filter would be "ipx". (Without the quotation marks) To see all packets that contain a Token-Ring RIF field, use "tr.rif". Fields can also be compared against values. The comparison operators can be expressed either through C-like symbols, or through English-like abbreviations: eq, == Equal ne, != Not equal gt, > Greater than lt, < Less Than ge, >= Greater than or Equal to le, <= Less than or Equal to Furthermore, each protocol field is typed. The types are: Unsigned integer (either 8-bit, 16-bit, 24-bit, or 32-bit) Signed integer (either 8-bit, 16-bit, 24-bit, or 32-bit) Boolean Ethernet address (6 bytes) Byte string (n-number of bytes) IPv4 address IPv6 address IPX network number String (text) Double-precision floating point number An integer may be expressed in decimal, octal, or hexadecimal notation. The following three display filters are equivalent: frame.pkt_len > 10 frame.pkt_len > 012 frame.pkt_len > 0xa Boolean values are either true or false. However, a boolean field is present in a protocol decode only if its value is true. If the value is false, the field is not presence. You can therefore check the truth value of a boolean field by simply checking for its existence, that is, by naming the field. For example, a token-ring packet's source route field is boolean. To find any source-routed packets, the display filter is simply: tr.sr Non source-routed packets can be found with the negation of that filter: ! tr.sr Ethernet addresses, as well as a string of bytes, are represented in hex digits. The hex digits may be separated by colons, periods, or hyphens: fddi.dst eq ff:ff:ff:ff:ff:ff ipx.srcnode == 0.0.0.0.0.1 eth.src == aa-aa-aa-aa-aa-aa If a string of bytes contains only one byte, then it is represented as an unsigned integer. That is, if you are testing for hex value 'ff' in a one-byte byte-string, you must compare it agains '0xff' and not 'ff'. IPv4 addresses can be represented in either dotted decimal notation, or by using the hostname: ip.dst eq www.mit.edu ip.src == 192.168.1.1 IPv4 address can be compared with the same logical relations as numbers: eq, ne, gt, ge, lt, and le. The IPv4 address is stored in host order, so you do not have to worry about how the endianness of an IPv4 address when using it in a display filter. Classless InterDomain Routing (CIDR) notation can be used to test if an IPv4 address is in a certain subnet. For example, this display filter will find all packets in the 129.111 Class-B network: ip.addr == 129.111.0.0/16 Remember, the number after the slash represents the number of bits used to represent the network. CIDR notation can also be used with hostnames, in this example of finding IP addresses on the same Class C network as 'sneezy': ip.addr eq sneezy/24 The CIDR notation can only be used on IP addresses or hostnames, not in variable names. So, a display filter like "ip.src/24 == ip.dst/24" is not valid. (yet) IPX networks are represented by unsigned 32-bit integers. Most likely you will be using hexadecimal when testing for IPX network values: ipx.srcnet == 0xc0a82c00 A substring operator also exists. You can check the substring (byte-string) of any protocol or field. For example, you can filter on the vendor portion of an ethernet address (the first three bytes) like this: eth.src[0:3] == 00:00:83 Or more simply, since the number of bytes is inherent in the byte-string you provide, you can provide just the offset. The previous example can be stated like this: eth.src[0] == 00:00:83 In fact, the only time you need to explicitly provide a length is when you don't provide a byte-string, and are comparing fields against fields: fddi.src[0:3] == fddi.dst[0:3] If the length of your byte-string is only one byte, then it must be represented in the same way as an unsigned 8-bit integer: llc[3] == 0xaa You can use the substring operator on a protocol name, too. And remember, the "frame" protocol encompasses the entire packet, allowing you to look at the nth byte of a packet regardless of its frame type (Ethernet, token-ring, etc.). token[0:5] ne 0.0.0.1.1 ipx[0:2] == ff:ff llc[3:1] eq 0xaa Offsets for byte-strings can also be negative, in which case the negative number indicates the number of bytes from the end of the field or protocol that you are testing. Here's how to check the last 4 bytes of a frame: frame[-4] == 0.1.2.3 or frame[-4:4] == 0.1.2.3 All the above tests can be combined together with logical expressions. These too are expressable in C-like syntax or with English-like abbreviations: and, && Logical AND or, || Logical OR xor, ^^ Logical XOR not, ! Logical NOT Expressions can be grouped by parentheses as well. The following are all valid display filter expression: tcp.port == 80 and ip.src == 192.168.2.1 not llc (ipx.srcnet == 0xbad && ipx.srnode == 0.0.0.0.0.1) || ip tr.dst[0:3] == 0.6.29 xor tr.src[0:3] == 0.6.29 A special caveat must be given regarding fields that occur more than once per packet. "ip.addr" occurs twice per IP packet, once for the source address, and once for the destination address. Likewise, tr.rif.ring fields can occur more than once per packet. The following two expressions are not equivalent: ip.addr ne 192.168.4.1 not ip.addr eq 192.168.4.1 The first filter says "show me all packets where an ip.addr exists that does not equal 192.168.4.1". That is, as long as one ip.addr in the packet does not equal 192.168.44.1, the packet passes the display filter. The second filter "don't show me any packets that have at least one ip.addr field equal to 192.168.4.1". If one ip.addr is 192.168.4.1, the packet does not pass. If B ip.addr fields is 192.168.4.1, then the packet passes. It is easy to think of the 'ne' and 'eq' operators as having an implict "exists" modifier when dealing with multiply-recurring fields. "ip.addr ne 192.168.4.1" can be thought of as "there exists an ip.addr that does not equal 192.168.4.1". Be careful with multiply-recurring fields; they can be confusing. The following is a table of protocol and protocol fields that are filterable in B. The abbreviation of the protocol or field is given. This abbreviation is what you use in the display filter. The type of the field is also given. =insert_dfilter_table =head1 FILES F and F<$HOME/.ethereal/preferences> contain system-wide and personal preference settings, respectively. The file contains preference settings of the form IB<:>I, one per line, where I is the name of the preference (which is the same name that would appear in the preference file), and I is the value to which it should be set; white space is allowed between B<:> and I. A preference setting can be continued on subsequent lines by indenting the continuation lines with white space. A B<#> character starts a comment that runs to the end of the line. The system-wide preference file is read first, if it exists, overriding B's default values; the personal preferences file is then read, if it exists, overriding default values and values read from the system-wide preference file. Note that whenever the preferences are saved by using the I button in the I dialog box, F<$HOME/.ethereal/preferences> will be overwritten with the new settings, destroying any comments that were in the file. F is consulted to correlate 6-byte hardware addresses to names. If an address is not found in F, the F<$HOME/.ethereal/ethers> file is consulted next. Each line contains one hardware address and name, separated by whitespace. The digits of the hardware address are separated by either a colon (:), a dash (-), or a period (.). The following three lines are valid lines of an ethers file: ff:ff:ff:ff:ff:ff Broadcast c0-00-ff-ff-ff-ff TR_broadcast 00.00.00.00.00.00 Zero_broadcast F matches the 3-byte vendor portion of a 6-byte hardware address with the manufacturer's name. The format of the file is the same as the F file, except that each address is three bytes instead of six. F and F<$HOME/.ethereal/ipxnets> correlate 4-byte IPX network numbers to names. The format is the same as the F file, except that each address if four bytes instead of six. Additionally, the address can be represented a single hexadecimal number, as is more common in the IPX world, rather than four hex octets. For example, these four lines are valid lines of an ipxnets file. C0.A8.2C.00 HR c0-a8-1c-00 CEO 00:00:BE:EF IT_Server1 110f FileServer3 =head1 SEE ALSO L, L =head1 NOTES The latest version of B can be found at B. =head1 AUTHORS Original Author -------- ------ Gerald Combs Contributors ------------ Gilbert Ramirez Hannes R. Boehm Mike Hall Bobo Rajec Laurent Deniel Don Lafontaine Guy Harris Simon Wilkinson Joerg Mayer Martin Maciaszek Didier Jorand Jun-ichiro itojun Hagino Richard Sharpe John McDermott Jeff Jahr Brad Robel-Forrest Ashok Narayanan Aaron Hillegass Jason Lango Johan Feyaerts Olivier Abad Thierry Andry Jeff Foster Peter Torvals Christophe Tronche Nathan Neulinger Tomislav Vujec Kojak Uwe Girlich Warren Young Heikki Vatiainen Greg Hankins Jerry Talkington Dave Chapeskie James Coe Bert Driehuis Stuart Stanley John Thomes Laurent Cazalet Thomas Parvais Gerrit Gehnen Craig Newell Ed Meaney Dietmar Petras Fred Reimer Florian Lohoff Jochen Friedrich Paul Welchinski Doug Nazar Andreas Sikkema Mark Muhlestein Graham Bloice Ralf Schneider Yaniv Kaul Paul Ionescu Mark Burton Stefan Raab Mark Clayton Michael Rozhavsky Dug Song Michael Tuexen Bruce Korb Jose Pedro Oliveira David Frascone Peter Kjellerstedt Phil Techau Wes Hardaker Robert Tsai Craig Metz Per Flock Jack Keane Brian Wellington Santeri Paavolainen Alain Magloire was kind enough to give his permission to use his version of snprintf.c. Dan Lasley gave permission for his dumpit() hex-dump routine to be used.