Thanks for your reply, Bill. > "ether proto \ip" is: <proto> <type> <id>
In what sense is "proto" here a <type>. <type>s are described as "qualifiers say what kind of thing the id name or number refers to. Possible types are host, net , port and portrange." Not only is "proto" not given as an option, but it seems to me as if it belongs in another category entirely. This leads to the more central question of how to match "\ip" with <id>. <id>s are defined in passing as "(name or number)". How can one match conceptually "\ip" with an address? I'm sorry to insist on this open-ended issue. I know there must be something off with my understanding, and would like to fix it if possible! Thanks again. Best regards, Ezequiel On Wed, Oct 17, 2012 at 4:49 PM, Bill Fenner <fen...@gmail.com> wrote: > On Wed, Oct 17, 2012 at 3:59 AM, Ezequiel Garzón > <garzon.luc...@gmail.com> wrote: >> Greetings! I'm trying to understand tcpdump expressions a bit more, >> and I'm confused about a basic example given in the pcap-filter man >> pages. They first state: >> >> | The filter expression consists of one or more primitives. Primitives >> usually consist of an id (name or number) preceded by one or more >> qualifiers. >> >> In turn, these qualifiers are type, dir and proto. So far so good, but >> further down we find this: >> >> | ip host host >> | which is equivalent to: >> | ether proto \ip and host host >> >> If I'm not mistaken, in the first case, ip and host are, respectively, >> proto and type. What pattern does 'ether proto \ip' follow? Isn't >> that, as a whole, a proto qualifier? If so, why isn't (a properly >> escaped) 'ether proto \ip host host' legal (without the keyboard >> 'and')? > > They're two separate primitives: > > "ether proto \ip" is: <proto> <type> <id> > > "host host" is <type> <id> > > Concatenating two primitives requires "and". > > (Don't get confused between "ether" being a <proto> and "proto" being > a <type>: that doesn't make "proto" a <proto>.) > > Bill _______________________________________________ tcpdump-workers mailing list tcpdump-workers@lists.tcpdump.org https://lists.sandelman.ca/mailman/listinfo/tcpdump-workers
