Commit | Line | Data |
---|---|---|
388db563 DC |
1 | ICMP host name utilities |
2 | ||
3 | Since the Linux kernel does not support the ICMP host name facilities as | |
4 | described in RFC 1788, I wrote a simple implementation in user-space. | |
5 | It comprises three parts: | |
6 | ||
7 | * icmpdnd – The ICMP Domain Name daemon, which listens to ICMP | |
8 | domain name requests and replies to them. | |
9 | ||
10 | * idnlookup – A user utility to query a host for its host name over | |
11 | ICMP. Like ping and all other utilities that use ICMP, it needs to | |
12 | be installed SUID root. | |
13 | ||
14 | * libnss_icmp.so.2 – A glibc NSS module, which uses idnlookup to | |
15 | perform queries for the gethostbyaddr function. | |
16 | ||
17 | General information | |
18 | ||
19 | The NSS module caches all requests (including failures) and honors the | |
20 | TTL value sent by the responding host. It uses a configuration file called | |
21 | /etc/nss-icmp.conf, which controls different aspects of its operation: | |
22 | ||
23 | * timeout – Sets the timeout in milliseconds for ICMP host name | |
24 | queries, by passing the -t option to idnlookup. | |
25 | * nocache – Disables the cache. | |
26 | * ttlnotfound – Sets the TTL for not-found cache entries is | |
27 | seconds. The default is 5 minutes. | |
28 | ||
29 | Both icmpdnd and idnlookup need to run as root, due to the fact that | |
30 | they use ICMP. Thus, idnlookup needs be installed SUID root. | |
31 |