core: 修复国内机器误判为 IPv6 不通

原因是用了 ping dnspod 公共 IPv6 DNS 作为连通性检测
但是这个 DNS 禁 ping

README.en.md

@@ -151,7 +151,7 @@ bash reinstall.sh centos      9
 
 ### Feature 2: DD
 
-- Supports `raw` `vhd` `gzip` and `xz` formatted images
+- Supports `raw`, `vhd`, `gzip` and `xz` formatted images
 - When using DD with a Windows image, the script will automatically expand the system partition. For static IP machines, the IP will be configured automatically, and it may take a few minutes to take effect on first boot
 
 ```bash

README.md

@@ -151,7 +151,7 @@ bash reinstall.sh centos      9
 
 ### 功能 2: DD
 
-- 支持 `raw` `vhd` `gzip`、`xz` 格式的镜像
+- 支持 `raw`、`vhd`、`gzip`、`xz` 格式的镜像
 - DD Windows 镜像时，会自动扩展系统盘。静态的机器会自动配置好 IP，可能首次开机几分钟后才生效
 
 ```bash

alpine-network.sh

@@ -10,10 +10,10 @@ ipv6_gateway=$5
 is_in_china=$6
 
 if $is_in_china; then
-    ipv4_dns1='119.29.29.29'
-    ipv4_dns2='223.5.5.5'
-    ipv6_dns1='2402:4e00::'
-    ipv6_dns2='2400:3200::1'
+    ipv4_dns1='223.5.5.5'
+    ipv4_dns2='119.29.29.29'
+    ipv6_dns1='2400:3200::1'
+    ipv6_dns2='2402:4e00::'
 else
     ipv4_dns1='1.1.1.1'
     ipv4_dns2='8.8.8.8'

reinstall.sh

@@ -247,8 +247,8 @@ test_url_real() {
     echo $url
     for i in $(seq 5 -1 0); do
         if command curl --insecure --connect-timeout 10 -Lfr 0-1048575 "$url" \
-            1> >(dd bs=1M count=1 of=$tmp_file iflag=fullblock 2>/dev/null) \
-            2> >(grep -v 'curl: (23)' >&2); then
+            1> >(exec dd bs=1M count=1 of=$tmp_file iflag=fullblock 2>/dev/null) \
+            2> >(exec grep -v 'curl: (23)' >&2); then
             break
         else
             ret=$?