fix: select correct primary IPv6 address whose subnet contains the gateway (#561)

* fix: select correct primary IPv6 address whose subnet contains the gateway

When a system has multiple IPv6 addresses with different prefix lengths
(e.g., /44 and /96), the script previously selected the first address
as primary regardless of whether its subnet contained the default gateway.
This caused the gateway to be unreachable after reinstallation.

This change:
- Adds pure shell expand_ipv6 and ip_addr_contains_gw functions to
  determine which IPv6 subnet contains the gateway (no python dependency)
- Modifies collect_netconf to select the correct primary IPv6 address
- Stores remaining addresses as ipv6_extra_addrs
- Adds extra IPv6 addresses via post-up in create_ifupdown_config

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix: address review feedback for IPv6 extra addrs and edge cases

- Pass ipv6_extra_addrs through initrd-network.sh (receive as $7,
  add extra addresses in add_missing_ipv6_config, write to netconf)
  so that trans.sh can read them via get_netconf_to
- Fix cut -c1-0 error when prefix_len < 4 in ip_addr_contains_gw
- Use grep -Fxve for exact string matching instead of regex

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix: use subshell for IFS modification to avoid leaking to outer scope

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix: avoid global IFS modification when iterating extra IPv6 addresses

Replace subshell IFS trick with tr+while read to split comma-separated
ipv6_extra_addrs, avoiding any modification of the IFS variable.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix: use ip route get instead of subnet matching for IPv6 primary address selection

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

initrd-network.sh

@@ -11,6 +11,7 @@ ipv4_gateway=$3
 ipv6_addr=$4
 ipv6_gateway=$5
 is_in_china=$6
+ipv6_extra_addrs=$7
 
 DHCP_TIMEOUT=15
 DNS_FILE_TIMEOUT=5
@@ -171,6 +172,15 @@ add_missing_ipv6_config() {
                 ip -6 route add default via "$ipv6_gateway" dev "$ethx" onlink
             fi
         fi
+
+        # 添加额外的 IPv6 地址（逗号分隔）
+        if [ -n "$ipv6_extra_addrs" ]; then
+            printf '%s\n' "$ipv6_extra_addrs" | tr ',' '\n' | while IFS= read -r addr; do
+                if [ -n "$addr" ]; then
+                    ip -6 addr add "$addr" dev "$ethx" 2>/dev/null || true
+                fi
+            done
+        fi
     fi
 }
 
@@ -506,5 +516,6 @@ echo "$ipv4_addr" >"$netconf/ipv4_addr"
 echo "$ipv4_gateway" >"$netconf/ipv4_gateway"
 echo "$ipv6_addr" >"$netconf/ipv6_addr"
 echo "$ipv6_gateway" >"$netconf/ipv6_gateway"
+echo "$ipv6_extra_addrs" >"$netconf/ipv6_extra_addrs"
 $ipv4_has_internet && echo 1 >"$netconf/ipv4_has_internet" || echo 0 >"$netconf/ipv4_has_internet"
 $ipv6_has_internet && echo 1 >"$netconf/ipv6_has_internet" || echo 0 >"$netconf/ipv6_has_internet"

reinstall.sh

@@ -2717,7 +2717,27 @@ collect_netconf() {
                 eval ipv${v}_ethx="$ethx" # can_use_cloud_kernel 要用
                 eval ipv${v}_mac="$(ip link show dev $ethx | grep link/ether | head -1 | awk '{print $2}')"
                 eval ipv${v}_gateway="$gateway"
-                eval ipv${v}_addr="$(ip -$v -o addr show scope global dev $ethx | grep -v temporary | head -1 | awk '{print $4}')"
+
+                # 获取所有全局地址
+                all_addrs=$(ip -$v -o addr show scope global dev $ethx | grep -v temporary | awk '{print $4}')
+                primary_addr=$(echo "$all_addrs" | head -1)
+
+                # IPv6: 用 ip route get 让内核返回正确的源 IP，指定 dev 避免 tun/warp 干扰
+                if [ "$v" = 6 ] && [ -n "$primary_addr" ]; then
+                    route_src=$(ip -6 route get 2001:4860:4860::8888 dev "$ethx" 2>/dev/null | grep -oP 'src \K[^ ]+')
+                    if [ -n "$route_src" ]; then
+                        for addr in $all_addrs; do
+                            if [ "${addr%/*}" = "$route_src" ]; then
+                                primary_addr=$addr
+                                break
+                            fi
+                        done
+                    fi
+                fi
+
+                eval ipv${v}_addr="$primary_addr"
+                # extra_addrs: 除主地址外的所有地址
+                eval ipv${v}_extra_addrs="$(echo "$all_addrs" | grep -Fxve "$primary_addr" | tr '\n' ',' | sed 's/,$//')"
             fi
         done
     fi
@@ -3607,13 +3627,13 @@ get_ip_conf_cmd() {
 
     sh=/initrd-network.sh
     if is_found_ipv4_netconf && is_found_ipv6_netconf && [ "$ipv4_mac" = "$ipv6_mac" ]; then
-        echo "'$sh' '$ipv4_mac' '$ipv4_addr' '$ipv4_gateway' '$ipv6_addr' '$ipv6_gateway' '$is_in_china'"
+        echo "'$sh' '$ipv4_mac' '$ipv4_addr' '$ipv4_gateway' '$ipv6_addr' '$ipv6_gateway' '$is_in_china' '$ipv6_extra_addrs'"
     else
         if is_found_ipv4_netconf; then
-            echo "'$sh' '$ipv4_mac' '$ipv4_addr' '$ipv4_gateway' '' '' '$is_in_china'"
+            echo "'$sh' '$ipv4_mac' '$ipv4_addr' '$ipv4_gateway' '' '' '$is_in_china' ''"
         fi
         if is_found_ipv6_netconf; then
-            echo "'$sh' '$ipv6_mac' '' '' '$ipv6_addr' '$ipv6_gateway' '$is_in_china'"
+            echo "'$sh' '$ipv6_mac' '' '' '$ipv6_addr' '$ipv6_gateway' '$is_in_china' '$ipv6_extra_addrs'"
         fi
     fi
 }

trans.sh

@@ -1121,6 +1121,16 @@ EOF
     post-up ip route add default via $ipv6_gateway dev $ethx
 EOF
             fi
+
+            # 额外的 IPv6 地址（子网不含网关的地址）
+            get_netconf_to ipv6_extra_addrs
+            if [ -n "$ipv6_extra_addrs" ]; then
+                _old_ifs=$IFS; IFS=','
+                for _addr in $ipv6_extra_addrs; do
+                    echo "    post-up ip -6 addr add $_addr dev $ethx" >>$conf_file
+                done
+                IFS=$_old_ifs
+            fi
         fi
 
         # dns