![wget 使用 ipv6 地址并且需要很长时间才能完成](https://linux22.com/image/113326/wget%20%E4%BD%BF%E7%94%A8%20ipv6%20%E5%9C%B0%E5%9D%80%E5%B9%B6%E4%B8%94%E9%9C%80%E8%A6%81%E5%BE%88%E9%95%BF%E6%97%B6%E9%97%B4%E6%89%8D%E8%83%BD%E5%AE%8C%E6%88%90.png)
在服务器上wget-1.16
需要 8 分钟才能完成:
$ wget http://http.debian.net/debian/dists/stable/Release -O -
--2017-06-12 23:44:40-- http://http.debian.net/debian/dists/stable/Release [4693/5569]
Resolving http.debian.net (http.debian.net)... 2001:4f8:1:c::15, 2605:bc80:3010:b00:0:deb:166:202, 2001:610:1908:b000::148:14, ...
Connecting to http.debian.net (http.debian.net)|2001:4f8:1:c::15|:80... failed: Connection timed out.
Connecting to http.debian.net (http.debian.net)|2605:bc80:3010:b00:0:deb:166:202|:80... failed: Connection timed out.
Connecting to http.debian.net (http.debian.net)|2001:610:1908:b000::148:14|:80... failed: Connection timed out.
Connecting to http.debian.net (http.debian.net)|140.211.166.202|:80... connected.
HTTP request sent, awaiting response... 302 Found
Location: http://cdn-fastly.deb.debian.org/debian/dists/stable/Release [following]
--2017-06-12 23:51:02-- http://cdn-fastly.deb.debian.org/debian/dists/stable/Release
Resolving cdn-fastly.deb.debian.org (cdn-fastly.deb.debian.org)... 2a04:4e42:3::204, 151.101.12.204
Connecting to cdn-fastly.deb.debian.org (cdn-fastly.deb.debian.org)|2a04:4e42:3::204|:80... failed: Connection timed out.
Connecting to cdn-fastly.deb.debian.org (cdn-fastly.deb.debian.org)|151.101.12.204|:80... connected.
...
因为它正在尝试使用 IPv6 地址进行连接。curl-7.38.0
在同一台机器上立即响应。因为它使用 IPv4 地址。他们解析域的方式不同吗?他们是如何做到的呢?如何wget
使用 IPv4 地址?
UPD
$ ip a
...
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether d8:cb:8a:37:cf:57 brd ff:ff:ff:ff:ff:ff
inet 188.40.99.4/26 brd 188.40.99.63 scope global eth0
valid_lft forever preferred_lft forever
inet6 2a01:4f8:100:738b::2/64 scope global
valid_lft forever preferred_lft forever
inet6 fe80::dacb:8aff:fe37:cf57/64 scope link valid_lft forever preferred_lft forever
$ ip route
default via 188.40.99.1 dev eth0
10.0.0.0/24 dev br0 proto kernel scope link src 10.0.0.1
188.40.99.0/26 via 188.40.99.1 dev eth0
188.40.99.0/26 dev eth0 proto kernel scope link src 188.40.99.4
答案1
curl
并且wget
不要使用不同的机制来解析域(他们正在使用getaddrinfo()
)。但是,curl
实施快速回退算法以在 IPv6 连接状况不佳的情况下改善用户体验。
RFC 6555(Happy Eyeballs)中详细描述了该算法:https://www.rfc-editor.org/rfc/rfc6555
根据curl/lib/connect.h
这个超时设置为200ms:https://github.com/curl/curl/blob/a8e523f086c12e7bb9acb18d1ac84d92dde0605b/lib/connect.h#L43
curl
和都wget
支持-4
/-6
选项,将分别强制连接到 IPv4 或 IPv6。