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Diffstat (limited to 'README.md')
| -rw-r--r-- | README.md | 85 |
1 files changed, 54 insertions, 31 deletions
@@ -14,50 +14,73 @@ This code is published with the license MIT (see LICENSE.txt) for details. functionality of the GNU C Library (`glibc`) providing host name resolution for *"localuser"* family of virtual hostnames. +It defines the family *"localuser"* of virtual hostnames as one of the +below names: + +- localuser +- localuser-UID +- localuser--APPID +- localuser-UID-APPID +- localuser---APPID + +This can be summarized by the following matrix: + + |------------------|------------------|---------------------|-------------------| + | | **current user** | **user of UID** | **no user** | + |------------------|------------------|---------------------|-------------------| + | **no APP** | localuser | localuser-UID | | + | **app of APPID** | localuser--APPID | localuser-UID-APPID | localuser---APPID | + |------------------|------------------|---------------------|-------------------| + The delivered NSS service defines one virtual host of name `localuser` that resolves to an IP address of the localhost loopback that integrates user ID. -It is intended to enable distinct IP for distinct users. - -The name "localuser" is resolved to the IPv4 address: +It is intended to enable distinct IP for distinct users, distinct application. -``` -127.x.y.z -``` +The name *localuser* family is resolved to the IPv4 address range 127.128.0.0/9 -where x.y.z encode the current user UID in such way that: +The delivered IPv4 address is structured as follow: -``` -UID = 65536*(x - 128) + 256*y + z +```text ++--------+--------+--------+--------+ +:01111111:1abbcccc:dddddeee:ffffffff: ++--------+--------+--------+--------+ ``` -Allowed UID are from 0 to 4194303 included. +When `a` is `1`, the value 11 bits value `bbccccddddd` encodes the APPID +and the 11 bits value `eeedddddddd` encodes the UID. +This is represented by the following hostnames: `localuser--APPID` +and `localuser-UID-APPID`. -And so: +When `abb` is `011`, the 20 bits value `ccccdddddeeeffffffff` encodes the APPID. +This is represented by the following hostnames: `localuser---APPID`. -``` -z = [0..255] -y = [0..255] -x = [128..191] -``` +When `abb` is `010`, the 20 bits value `ccccdddddeeeffffffff` encodes the UID. +This is represented by the following hostnames: `localuser` +and `localuser-UID`. -The names "localuser-${UID}", where UID is a decimal number, are resolved to addresses: +The values `000` and `001` of `abb` are reserved for futur use. -``` -127.x.y.z +Examples: -z = UID % 255 -y = (UID >> 8) % 256 -x = ((UID >> 16) % 256) + 128 -``` +```text +localuser => 127.160.0.0 (when user has UID = 0) +localuser => 127.160.3.233 (when user has UID = 1001) -Examples: +localuser-0 => 127.160.0.0 +localuser-45 => 127.160.0.45 +localuser-1024 => 127.160.4.0 +localuser-1048575 => 127.175.255.255 -``` -localuser => 127.128.0.0 (when user has UID = 0) -localuser => 127.128.3.233 (when user has UID = 1001) -localuser-1024 => 127.128.4.0 (for any user) +localuser---0 => 127.176.0.0 +localuser---45 => 127.176.0.45 +localuser---1048575 => 127.191.255.255 + +localuser-0-0 => 127.192.0.0 +localuser--78 => 127.194.115.233 (when user has UID = 1001) +localuser-23-54 => 127.193.176.23 +localuser-2047-2047 => 127.255.255.255 ``` The service also provides the reverse resolution. @@ -67,7 +90,7 @@ because IPv6 lacks of loopback range. Example: -``` +```text localuser-1024 => ::ffff:127.128.4.0 ``` @@ -78,7 +101,7 @@ For details about NSS integration, see To install this file: -``` +```sh make all && sudo install ``` @@ -88,7 +111,7 @@ script detect-nssdir.sh. If the script detect-nssdir.sh gives the wrong result, just define the variable nssdir when calling make, as below: -``` +```sh make install nssdir=~/lib ``` |