.TH SNOOPY 8 .SH NAME snoopy \- spy on network packets .SH SYNOPSIS .B snoopy [ .B -?stdCp ] [ .B -f .I filter-expression ] [ .B -N .I n ] [ .B -h first-header ] [ packet-file ] .SH DESCRIPTION .PP .I Snoopy reads packets from a packet source (default .BR /net/ether0 ), matches them to a filter (by default anything matches), and writes matching packets to standard output either in human readable form (default) or in a binary trace format that can be reinput to .IR snoopy . .PP The human readable format consists of multiple lines per packet. The first line contains the milliseconds since the trace was started. Subsequent ones are indented with a tab and each contains the dump of a single protocol header. The last line contains the dump of any contained data. For example, a .SM BOOTP packet would look like: .sp .EX 324389 ms ether(s=0000929b1b54 d=ffffffffffff pr=0800 ln=342) ip(s=135.104.9.62 d=255.255.255.255 id=5099 frag=0000... udp(s=68 d=67 ck=d151 ln= 308) bootp(t=Req ht=1 hl=16 hp=0 xid=217e5f27 sec=0 fl=800... dhcp(t=Request clientid=0152415320704e7266238ebf01030... .EE .PP The binary format consists of: .IP 2 bytes of packet length, msb first .IP 8 bytes of nanosecond time, msb first .IP the packet .PP Filters are expressions specifying protocols to be traced and specific values for fields in the protocol headers. The grammar is: .sp .EX expr : protocol | field '=' value | protocol '(' expr ')' | '(' expr ')' | expr '||' expr | expr '&&' expr | '!' expr .EE .PP The values for and can be obtained using the .B -? option. It will list each known protocol, which subprotocols it can multiplex to, and which fields can be used for filtering. For example, the listing for ethernet is currently: .sp .EX ether's filter attr: s - source address d - destination address a - source|destination address t - type ether's subprotos: ip arp rarp ip6 pppoe_disc pppoe_sess .EE .PP The format of depends on context. In general, ethernet addresses are entered as a string of hex digits; IP numbers in the canonical `.' format for v4 and `:' format for v6; and ports in decimal. .PP .IR Snoopy 's options are: .TP .B -t input is a binary trace file. The default assumes a packet device, one packet per read. .TP .B -d output will be a binary trace file. The default is human readable. .TP .B -s force one output line per packet. The default is multiline. .TP .B -C compute correct checksums and if doesn't match the contained one, add a field .B !ck=\fIxxxx\fP where .I xxxx is the correct checksum. .TP .B -p do not enter promiscuous mode. Only packets to this interface will be seen. .TP .B -N dump .I n data bytes per packet. The default is 32. .TP .B -f use .I filter-expression to filter the packet stream. The default is to match all packets. .TP .B -h assume the first header per packet to be .IR first-header . The default is .IR ether . .SH EXAMPLES the following would display only .SM BOOTP and .SM ARP packets: .sp .EX % snoopy -f 'arp || bootp' after optimize: ether( arp || ip( udp( bootp ) ) ) .EE .PP The first line of output shows the completed filter expression. .I Snoopy will fill in other protocols as necessary to complete the filter and then optimize to remove redundant comparisons. .PP To save all packets between 135.104.9.2 to 135.104.9.6 and later display those to/from TCP port 80: .sp .EX % ramfs % snoopy -df 'ip(s=135.104.9.2&&d=135.104.9.6)||\\ ip(s=135.104.9.6&&d=135.104.9.2)' > /tmp/quux % snoopy -tf 'tcp(sd=80)' /tmp/quux .EE .SH FILES .TP .B /net/ether Ethernet device .SH SOURCE .B /sys/src/cmd/ip/snoopy .SH BUGS At the moment it only dumps ethernet packets because there's no device to get IP packets without the media header. This will be corrected soon.