Previously, a single `icmp_conn` record was built per ICMP "connection"
and re-used for all events generated from it. This may have been a
historical attempt at performance optimization, but:
* By default, Zeek does not load any scripts that handle ICMP events.
* The one script Zeek ships with that does handle ICMP events,
"detect-traceroute", is already noted as being disabled due to
potential performance problems of doing that kind of analysis.
* Re-use of the original `icmp_conn` record tends to misreport
TTL and length values since they come from original packet instead
of the current one.
* Even if we chose to still re-use `icmp_conn` records and just fill
in a new TTL and length value each packet, a user script could have
stored a reference to the record and not be expecting those values
to be changed out from underneath them.
Now, a new `icmp_info` record is created/populated in all ICMP events
and should be used instead of `icmp_conn`. It also removes the
orig_h/resp_h fields as those are redundant with what's already
available in the connection record.
With this patch the model is:
- "print" cleans the data so that non-printable characters get
escaped. This is not necessarily reversible.
- to print in a reversible way, one can go through
escape_string(); this escapes backslashes as well to make the
decoding non-ambigious.
- Logging always escapes similar to escape_string(), making it
reversible.
Compared to master, we also change the escaping as follows:
- We now only escape with "\xXX", no more "^X" or "\0". Exception:
backslashes.
- We escape backlashes as "\\".
- There's no "alternative" output style anymore, i.e., fmt() '%A'
qualifier is gone.
Baselines in testing/btest are updated, external tests not yet.
Addresses BIT-1333.
- The 'icmp_conn' record now contains an 'hlim' field since hop limit
in the IP header is an interesting field for at least these ND
messages.
- Changed 'icmp_router_advertisement' event parameters.
'router_lifetime' is now an interval. Fix 'reachable_time' and
'retrans_timer' using wrong internal Val type for intervals.
Made more of the known router advertisement flags available through
boolean parameters.
- Changed 'icmp_neighbor_advertisement' event parameters to add
more of the known boolean flags.
- Add more guards against trying to analyze captured packets with a
truncated IPv6 static header or extension header chain.
- Add back in the ICMP payload tracking for ICMP "connections".
- Fix 'icmp_context' record construction. Some field assignments
were mismatched for ICMP and ICMP6. Source and destination
addresses were set incorrectly for context packets that don't
contain a full IP header. Some fields for ICMP6 weren't filled out.
- Changed ICMP Time Exceeded packets to raise the 'icmp_time_exceeded'
event instead of 'icmp_error_message'.
- Add unit tests for truncation and the main types of ICMP/ICMP6
that have specific events.
- Documentation clarifications.
