| Long: happy-eyeballs-timeout-ms |
| Arg: <milliseconds> |
| Help: How long to wait in milliseconds for IPv6 before trying IPv4 |
| Added: 7.59.0 |
| --- |
| Happy eyeballs is an algorithm that attempts to connect to both IPv4 and IPv6 |
| addresses for dual-stack hosts, preferring IPv6 first for the number of |
| milliseconds. If the IPv6 address cannot be connected to within that time then |
| a connection attempt is made to the IPv4 address in parallel. The first |
| connection to be established is the one that is used. |
| |
| The range of suggested useful values is limited. Happy Eyeballs RFC 6555 says |
| "It is RECOMMENDED that connection attempts be paced 150-250 ms apart to |
| balance human factors against network load." libcurl currently defaults to |
| 200 ms. Firefox and Chrome currently default to 300 ms. |
| |
| If this option is used several times, the last one will be used. |
