# Debian网络异常和日志查看命令记录
## 1. 手动协商命令
```bash
ethtool -r lan2
```

## 2. WatchDog日志查看。

看最近运行日志
```bash
journalctl -u lan2-link-watchdog.service -n 100 --no-pager
```

实时看：
```bash
journalctl -u lan2-link-watchdog.service -f
```
只看有没有触发过重新协商

这个最有用：
```bash
journalctl -u lan2-link-watchdog.service --no-pager | grep -E 'BAD|ACTION|VERIFY|cooldown'
```
如果没输出，说明从启动到现在没有触发过异常处理。

如果触发过，会看到类似：
```bash
BAD round 1/2: received 92/100, loss=8
BAD round 2/2: received 90/100, loss=10
ACTION: renegotiate lan2 because link quality is bad
VERIFY after renegotiate: received 100/100
cooldown 300s
```
其中关键是这行：
```bash
ACTION: renegotiate lan2 because link quality is bad
```
看到它就说明 watchdog 执行过：
```bash
ethtool -r lan2
```
看今天触发过几次
```bash
journalctl -u lan2-link-watchdog.service --since today --no-pager | grep -c 'ACTION: renegotiate'
```
输出 0 就是今天没触发。

看当前这次开机以来有没有触发
```bash
journalctl -b -u lan2-link-watchdog.service --no-pager | grep -E 'BAD|ACTION|VERIFY|cooldown'
```
看当前状态
```bash
systemctl status lan2-link-watchdog.service --no-pager
```
另外，因为脚本里有这句：
```bash
logger -t lan2-watchdog "$*"
```
所以你也可以按 tag 查：
```bash
journalctl -t lan2-watchdog --no-pager
```
不过平时用这个就够了：
```bash
journalctl -u lan2-link-watchdog.service --no-pager | grep -E 'BAD|ACTION|VERIFY|cooldown'
```
如果以后重启后想保留更久的日志，可以确认一下 journald 是否持久化：
```bash
journalctl --list-boots
```
如果能看到多次 boot 记录，说明日志是保留的。否则以后我再帮你改成单独写 /var/log/lan2-link-watchdog.log 也行。

## 3. 创建 lan3 watchdog 脚本
```bash
sudo tee /usr/local/sbin/lan3-link-watchdog.sh >/dev/null <<'EOF'
#!/bin/bash

IFACE="lan3"
CHECK_IFACE="lan3"
GW="192.168.3.1"

COUNT=100
MIN_RECV=99             # RECV < 99 才算异常；也就是 98/100 或更低
BAD_ROUNDS_LIMIT=2      # 连续 2 轮异常才执行 ethtool -r
SLEEP_OK=60             # 正常时，每轮结束后休息 60 秒
COOLDOWN=300            # 重协商后冷却 300 秒
ARPING_TIMEOUT=130      # arping 100 次大约 100 秒，给 130 秒超时

BAD_ROUNDS=0

log() {
    logger -t lan3-watchdog "$*"
    echo "$(date '+%F %T') $*"
}

ARPING_BIN="$(command -v arping || true)"
ETHTOOL_BIN="$(command -v ethtool || true)"

if [ -z "$ARPING_BIN" ]; then
    log "ERROR: arping not found"
    exit 1
fi

if [ -z "$ETHTOOL_BIN" ]; then
    log "ERROR: ethtool not found"
    exit 1
fi

log "started: IFACE=$IFACE CHECK_IFACE=$CHECK_IFACE GW=$GW COUNT=$COUNT MIN_RECV=$MIN_RECV BAD_ROUNDS_LIMIT=$BAD_ROUNDS_LIMIT"

while true; do
    if [ ! -d "/sys/class/net/$IFACE" ]; then
        log "WARN: interface $IFACE not found, sleep ${SLEEP_OK}s"
        sleep "$SLEEP_OK"
        continue
    fi

    if [ ! -d "/sys/class/net/$CHECK_IFACE" ]; then
        log "WARN: check interface $CHECK_IFACE not found, sleep ${SLEEP_OK}s"
        sleep "$SLEEP_OK"
        continue
    fi

    OUT=$(LANG=C timeout "$ARPING_TIMEOUT" "$ARPING_BIN" -I "$CHECK_IFACE" -c "$COUNT" "$GW" 2>&1)

    SENT=$(echo "$OUT" | awk '/^Sent / {print $2}')
    RECV=$(echo "$OUT" | awk '/^Received / {print $2}')

    if [ -z "$RECV" ]; then
        BAD_ROUNDS=$((BAD_ROUNDS + 1))
        log "WARN: could not parse arping result, bad round $BAD_ROUNDS/$BAD_ROUNDS_LIMIT"
        log "$OUT"

        if [ "$BAD_ROUNDS" -ge "$BAD_ROUNDS_LIMIT" ]; then
            log "ACTION: renegotiate $IFACE because arping result could not be parsed repeatedly"
            "$ETHTOOL_BIN" -r "$IFACE"

            BAD_ROUNDS=0
            log "cooldown ${COOLDOWN}s"
            sleep "$COOLDOWN"
        else
            sleep "$SLEEP_OK"
        fi

        continue
    fi

    LOSS=$((COUNT - RECV))

    if [ "$RECV" -gt "$COUNT" ]; then
        log "OK with extra replies: received $RECV/$COUNT, likely another arping is running"
        BAD_ROUNDS=0
        sleep "$SLEEP_OK"
        continue
    fi

    if [ "$RECV" -lt "$MIN_RECV" ]; then
        BAD_ROUNDS=$((BAD_ROUNDS + 1))
        log "BAD round $BAD_ROUNDS/$BAD_ROUNDS_LIMIT: received $RECV/$COUNT, loss=$LOSS"

        if [ "$BAD_ROUNDS" -ge "$BAD_ROUNDS_LIMIT" ]; then
            log "ACTION: renegotiate $IFACE because link quality is bad"
            "$ETHTOOL_BIN" -r "$IFACE"

            sleep 5

            VERIFY=$(LANG=C timeout "$ARPING_TIMEOUT" "$ARPING_BIN" -I "$CHECK_IFACE" -c "$COUNT" "$GW" 2>&1)
            VERIFY_RECV=$(echo "$VERIFY" | awk '/^Received / {print $2}')

            log "VERIFY after renegotiate: received ${VERIFY_RECV:-unknown}/$COUNT"

            BAD_ROUNDS=0
            log "cooldown ${COOLDOWN}s"
            sleep "$COOLDOWN"
        else
            sleep "$SLEEP_OK"
        fi
    else
        if [ "$BAD_ROUNDS" -ne 0 ]; then
            log "RECOVERED without action: received $RECV/$COUNT"
        fi

        log "OK: received $RECV/$COUNT"
        BAD_ROUNDS=0
        sleep "$SLEEP_OK"
    fi
done
EOF
```
给脚本赋权限
```bash
sudo chmod +x /usr/local/sbin/lan3-link-watchdog.sh
```

## 4. 创建 lan3 systemd 服务
```bash
sudo tee /etc/systemd/system/lan3-link-watchdog.service >/dev/null <<'EOF'
[Unit]
Description=Watch lan3 link quality and renegotiate on packet loss
After=network-online.target
Wants=network-online.target

[Service]
Type=simple
ExecStart=/usr/local/sbin/lan3-link-watchdog.sh
Restart=always
RestartSec=10

[Install]
WantedBy=multi-user.target
EOF
```
然后加载一下：
```bash
sudo systemctl daemon-reload
```
确认 lan3 通了之后，再启用：
```bash
sudo systemctl enable lan3-link-watchdog.service
sudo systemctl start lan3-link-watchdog.service
```