mirror of
https://github.com/tonusoo/koduinternet-cpe
synced 2024-12-05 01:00:59 +02:00
115 lines
3.0 KiB
Plaintext
115 lines
3.0 KiB
Plaintext
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#!/usr/bin/env bash
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# Title : isp-switch
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# Last modified date : 30.05.2023
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# Author : Martin Tonusoo
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# Description : Script pings anycast DNS servers IPv4 addresses
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# using a primary connection(wan0; Telia fiber) and
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# if none of those replies, then switches v4 default
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# route to backup connection(wwan0; Telia mobile
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# broadband). Once the primary connection restores,
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# the v4 default route is switched back to primary
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# connection.
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# Options :
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# Notes : "ignore_routes_with_linkdown" settings in
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# /etc/sysctl.conf ensure that the route is
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# instantly ignored if its link is down.
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ping_check() {
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ping_success=0
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for ip in 1.1.1.1 8.8.8.8 9.9.9.9; do
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# Even if one ping out of four succeeds, then
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# the exit code is 0.
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ping -I "$1" -W 1 -c 4 -q "$ip" &>/dev/null
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ping_success=$(( ping_success + $? ))
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done
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if (( ping_success >= 3 )); then
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# All 12 pings failed.
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return 1
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else
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return 0
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fi
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}
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read -r ip_regex << EOF
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^((25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]?|0)\.){3}\
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(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]?|0)$
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EOF
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while true; do
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sleep 1
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read -r _ _ wan0_gw _ wan0_metric _ <<-EOF
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$(ip -4 -o route show default dev wan0 2>/dev/null | grep -v " linkdown")
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EOF
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read -r _ _ wwan0_gw _ wwan0_metric _ <<-EOF
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$(ip -4 -o route show default dev wwan0 2>/dev/null | grep -v " linkdown")
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EOF
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# There is no point to proceed if both or one of the default
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# routes is missing. In addition, sanity check the next hop
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# address.
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if ! { [[ "$wan0_gw" =~ $ip_regex ]] || [[ "$wwan0_gw" =~ $ip_regex ]]; }; then
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echo "No default route found."
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continue
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elif ! [[ "$wan0_gw" =~ $ip_regex ]]; then
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echo "Primary default route via wan0 is missing."
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continue
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elif ! [[ "$wwan0_gw" =~ $ip_regex ]]; then
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echo "Failover default route via wwan0 is missing."
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continue
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fi
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# Default IPv4 route metric is 0.
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if (( ${wan0_metric:-0} < ${wwan0_metric:-0} )); then
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if ! ping_check wan0; then
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# Ping check on primary connection failed.
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echo "Switching to backup via $wwan0_gw dev wwan0"
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ip -4 route flush default
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ip -4 route add default via "$wwan0_gw" dev wwan0 metric 100
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ip -4 route add default via "$wan0_gw" dev wan0 metric 200
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fi
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else
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# Backup connection is in use. Check if it is possible
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# to switch back to primary connection.
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ip -4 route add default via "$wan0_gw" table 100
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# Specifying the "priority" ensures that there are
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# no duplicate rules created.
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ip rule add oif wan0 lookup 100 priority 100
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if ping_check wan0; then
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# Ping check on primary connection succeeded.
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echo "Switching to primary via $wan0_gw dev wan0"
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ip -4 route flush default
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ip -4 route add default via "$wan0_gw" dev wan0 metric 100
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ip -4 route add default via "$wwan0_gw" dev wwan0 metric 200
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fi
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ip -4 route flush table 100
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ip rule delete oif wan0 lookup 100 priority 100
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fi
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done
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