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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 | ||
ca034738 | 7 | * icmpdnd - The ICMP Domain Name daemon, which listens to ICMP |
388db563 DC |
8 | domain name requests and replies to them. |
9 | ||
ca034738 | 10 | * idnlookup - A user utility to query a host for its host name over |
388db563 DC |
11 | ICMP. Like ping and all other utilities that use ICMP, it needs to |
12 | be installed SUID root. | |
13 | ||
ca034738 | 14 | * libnss_icmp.so.2 - A glibc NSS module, which uses idnlookup to |
388db563 DC |
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 | ||
ca034738 | 23 | * timeout - Sets the timeout in milliseconds for ICMP host name |
388db563 | 24 | queries, by passing the -t option to idnlookup. |
ca034738 DC |
25 | * nocache - Disables the cache. |
26 | * ttlnotfound - Sets the TTL for not-found cache entries is | |
388db563 DC |
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 |