1 Glibc IPv4

tengel edited this page 2024-03-20 11:55:03 -05:00

Glibc provides the capability per RFC 3484 to allow the sysadmin to specify the sort order of returned calls to getaddrinfo() via the /etc/gai.conf file. This is a handy way to have IPv4 preferred over IPv6 returned addresses:

precedence  ::ffff:0:0/96  100

The presence of a single precedence line in the configuration file causes the default table to not be used. The /etc/gai.conf is typically either empty or missing; if configured in the file the default table would look like:

/etc/gai.conf (RFC defaults)

label       ::1/128        0
label       ::/0           1
label       2002::/16      2
label       ::/96          3
label       ::ffff:0:0/96  4
precedence  ::1/128        50
precedence  ::/0           40
precedence  2002::/16      30
precedence  ::/96          20
precedence  ::ffff:0:0/96  10

When adding the IPv4 precedence, change the last line to indicate 100 (larger number == higher precedence):

/etc/gai.conf (IPv4 preferred)

label       ::1/128        0
label       ::/0           1
label       2002::/16      2
label       ::/96          3
label       ::ffff:0:0/96  4
precedence  ::1/128        50
precedence  ::/0           40
precedence  2002::/16      30
precedence  ::/96          20
precedence  ::ffff:0:0/96  100

Index

• APT WhatProvides
• Apache wpadmin
• Arch Default Kernel
• Arch Kernel Order
• Bash Add fd
• Bash Dump History
• Bash Trim Whitespace
• CPU Stats
• CSS Reset
• DB2 Info
• Debian Upgrade
• Dell OpenManage
• Diff Lines
• Favicon Things
• Find Examples
• Forgejo Syntax Highlight
• Git Combine Repos
• Git Multi SSH
• Git Quickstart
• Git Rewrite User
• Gitea Mirror
• GitLab Anchors
• Glibc IPv4
• GnuPG Things
• IMAP Sync
• IPv4 Default Gateway
• IPv4 Default IP
• KRB5 Empty Keytab
• Kernel Boot Debug
• Kernel Decompress
• LUKS Encrypted Partitions
• Linux Valid Usernames
• Loopback FS
• MP3 Get Tags
• MX Tarpit
• Makefile Template
• Markdown Samples
• Mount OVA
• Mount qcow2
• MySQL Connections
• NFS 10G Tuning
• Netcat Replacements
• PAM Namespace
• Postfix Headers
• Proxmox Doodads
• RPM Info
• Radeon Temperature
• Recover Deleted ext3
• Recursive Unzip
• Roku Info
• SSH RSA Support
• SSL Certgen
• Samba OSX
• Server Notes
• Smem Datamash
• Split Disk
• systemd PID1
• TCP Kill
• Thunderbird LDAP AD
• uBlock Filters
• udev Hide Partitions
• Weechat Quickstart
• YTM to Textbox
• YUM Disablerepos

• SPDX-License-Identifier: CC-BY-SA-4.0
• SPDX-License-Identifier: MIT