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Update tailgate-allow@.service with PMTUD support #3

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Update tailgate-allow@.service with PMTUD support #3

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21 changes: 21 additions & 0 deletions systemd/tailgate-allow@.service
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,17 @@ ExecStartPre=/bin/sh -c 'INTERFACE=%i; PORT=$(cat /run/tailgate-%i.port); \
iptables -C tailgate -o $INTERFACE -p udp --sport $PORT -j ACCEPT > /dev/null 2>&1 || \
iptables -I tailgate -o $INTERFACE -p udp --sport $PORT -j ACCEPT'

# Allow Essential ICMP Traffic for PMTUD
ExecStartPre=/bin/sh -c 'iptables -I OUTPUT -p icmp --icmp-type fragmentation-needed -j ACCEPT'
ExecStartPre=/bin/sh -c 'iptables -I OUTPUT -p icmp --icmp-type echo-request -j ACCEPT'
ExecStartPre=/bin/sh -c 'iptables -I OUTPUT -p icmp --icmp-type echo-reply -j ACCEPT'
ExecStartPre=/bin/sh -c 'iptables -I INPUT -p icmp --icmp-type fragmentation-needed -j ACCEPT'
ExecStartPre=/bin/sh -c 'iptables -I INPUT -p icmp --icmp-type echo-request -j ACCEPT'
ExecStartPre=/bin/sh -c 'iptables -I INPUT -p icmp --icmp-type echo-reply -j ACCEPT'

# Implement MSS Clamping
ExecStartPre=/bin/sh -c 'iptables -t mangle -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu'

ExecStart=/bin/sh -c 'REAL_PORT=$(cat /run/tailgate-%i.port); rm /run/tailgate-%i.port; \
if [ "$REAL_PORT" -eq 41641 ]; then exit 0; fi; \
while true; do PORT=$(ss -lunp4 | awk "/tailscale/ {split(\\$4, arr, \\":\\"); print arr[2]}"); \
Expand All @@ -34,6 +45,16 @@ ExecStopPost=-/bin/sh -c '{ [ $(iptables -L tailgate 2>/dev/null | wc -l) -le 2
iptables -D OUTPUT -j tailgate && \
iptables -X tailgate; } || true'

# Cleanup ICMP and MSS Clamping Rules on Service Stop
ExecStopPost=-/bin/sh -c 'iptables -D OUTPUT -p icmp --icmp-type fragmentation-needed -j ACCEPT || true'
ExecStopPost=-/bin/sh -c 'iptables -D OUTPUT -p icmp --icmp-type echo-request -j ACCEPT || true'
ExecStopPost=-/bin/sh -c 'iptables -D OUTPUT -p icmp --icmp-type echo-reply -j ACCEPT || true'
ExecStopPost=-/bin/sh -c 'iptables -D INPUT -p icmp --icmp-type fragmentation-needed -j ACCEPT || true'
ExecStopPost=-/bin/sh -c 'iptables -D INPUT -p icmp --icmp-type echo-request -j ACCEPT || true'
ExecStopPost=-/bin/sh -c 'iptables -D INPUT -p icmp --icmp-type echo-reply -j ACCEPT || true'

ExecStopPost=-/bin/sh -c 'iptables -t mangle -D FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu || true'

Type=oneshot
Restart=on-failure
RemainAfterExit=yes