增加magisk模块功能：热点局域网转发。 (#1252)

* 增加magisk模块功能：热点局域网转发。该功能由后台监控，热点打开，可自动增加转发规则。在三星fold3测试通过。

* 增加了默认tun名称的识别

1.防止配置文件没有配置dev_name的情况，按默认名称tun+在网络设备中查找；
2.一旦热点关闭，自动删除规则。

* 考虑到主程序已可通过模块开关来重新加载，将操作按钮用于转发开关。此外对状态栏信息进行了一些修饰，加入了转发状态的显示。

easytier-contrib/easytier-magisk/hotspot_iprule.sh

@@ -0,0 +1,90 @@
+#!/system/bin/sh
+MODDIR=${0%/*}
+CONFIG_FILE="${MODDIR}/config/config.toml"
+LOG_FILE="${MODDIR}/log.log"
+ACTION="$1"  # 参数：add add_once del
+
+
+# 获取接口/IP
+get_et_iface() {
+    awk '
+        BEGIN { IGNORECASE = 1 }
+        /^[[:space:]]*dev_name[[:space:]]*=/ {
+            val = $0
+            sub(/^[^=]*=[[:space:]]*/, "", val)
+            gsub(/[" \t]/, "", val)
+            print val
+            exit
+        }
+    ' "$CONFIG_FILE"
+}
+get_tun_iface() {
+    ip link | awk -F': ' '/ tun[[:alnum:]]+/ {print $2; exit}'
+}
+get_hot_iface() {
+    ip link | awk -F': ' '/(^| )(swlan[[:alnum:]_]*|softap[[:alnum:]_]*|ap[[:alnum:]_]*)\:/ {print $2; exit}' | cut -d'@' -f1 | head -n1
+}
+get_hot_cidr() {
+    ip -4 addr show dev "$1" | awk '/inet /{print $2; exit}'
+}
+
+
+set_nat_rules() {
+    ET_IFACE=$(get_et_iface)
+    [ -z "$ET_IFACE" ] && ET_IFACE="$(get_tun_iface)"
+    HOT_IFACE=$(get_hot_iface)
+    HOT_CIDR=$(get_hot_cidr "$HOT_IFACE")
+
+    # 如果热点关闭就删除自定义链
+    [ -n "$ET_IFACE" ] && [ -n "$HOT_CIDR" ] || return 1
+
+    # 创建自定义链（如不存在）
+    iptables -t nat -N ET_NAT 2>/dev/null
+    iptables -N ET_FWD 2>/dev/null
+
+    # 确保主链首条跳转到自定义链
+    iptables -t nat -C POSTROUTING -j ET_NAT 2>/dev/null || \
+        iptables -t nat -I POSTROUTING 1 -j ET_NAT
+    iptables -C FORWARD -j ET_FWD 2>/dev/null || \
+        iptables -I FORWARD 1 -j ET_FWD
+
+    # 添加规则
+    iptables -t nat -A ET_NAT -s "$HOT_CIDR" -o "$ET_IFACE" -j MASQUERADE
+    iptables -A ET_FWD -i "$HOT_IFACE" -o "$ET_IFACE" \
+        -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT
+    iptables -A ET_FWD -i "$ET_IFACE" -o "$HOT_IFACE" \
+        -m state --state ESTABLISHED,RELATED -j ACCEPT
+
+    echo "[ET-NAT] Rules applied: $HOT_IFACE $HOT_CIDR ↔ $ET_IFACE" >> "$LOG_FILE"
+}
+
+flush_rules() {
+    iptables -t nat -F ET_NAT 2>/dev/null
+    iptables -F ET_FWD 2>/dev/null
+    echo "[ET-NAT] Custom chains flushed." >> "$LOG_FILE"
+}
+
+case "$ACTION" in
+    add)
+        set_nat_rules
+        echo "[ET-NAT] Guard started." >> "$LOG_FILE"
+        ip monitor link addr | while read -r _; do
+            if [ -f "${MODDIR}/enable_IP_rule" ]; then
+                flush_rules
+                set_nat_rules
+            fi
+        done
+        ;;
+    add_once)
+        flush_rules
+        set_nat_rules
+        echo "[ET-NAT] One-time rules applied." >> "$LOG_FILE"
+        ;;
+    del)
+        flush_rules
+        ;;
+    *)
+        echo "Usage: $0 [add|del]"
+        exit 1
+        ;;
+esac