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Direct set TCPMSS in ip tables #6

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Direct set TCPMSS in ip tables #6

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5969fb1
Add option to set the MSS value through iptables
matuszeg Mar 5, 2023
e7722b1
Add debug version of MSS iptables modification
matuszeg Mar 5, 2023
59d81c1
make scripts executable
matuszeg Mar 5, 2023
dbc2074
Reverse the check for MTU in /etc/ppp/peers/* because it appears to b…
matuszeg Mar 5, 2023
d7635cc
change code that updates /etc/ppp/peers/* to match any pre-existing m…
matuszeg Mar 5, 2023
f0cd906
update to use the variable value correctly, it needs quotes
matuszeg Mar 5, 2023
af989be
check to see if we have target mtu for /etc/ppp/peers/* rather than c…
matuszeg Mar 5, 2023
67b0408
check for eth interface having correct value rather than not having i…
matuszeg Mar 5, 2023
2a7b9b1
add message for already having the correct mss value
matuszeg Mar 5, 2023
b76d112
when verifying the running mtu, check against the correct value rathe…
matuszeg Mar 5, 2023
6a02ce1
delay the config change restart of pppd until after the eth interface…
matuszeg Mar 5, 2023
00130e8
Match changes made in the debug file
matuszeg Mar 5, 2023
d38ce68
return default to 1500
matuszeg Mar 5, 2023
780e3e6
isolate the SET_MSS changes
matuszeg Mar 5, 2023
ddfcb3f
isolate set_mss changes
matuszeg Mar 5, 2023
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Empty file modified 10-monitor-ppp-mtu.sh
100644 → 100755
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17 changes: 17 additions & 0 deletions 11-change-ppp-mtu-debug.sh
100644 → 100755
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@
MINTERFACES="(ppp0)"
# Desired MTU of PPP interfaces
PTARGET=1500
SET_MSS=FALSE

runningmtu=0
restartpppd=0
Expand Down Expand Up @@ -82,6 +83,22 @@ while true; do
fi
fi
done

if [[ $SET_MSS ]]; then
echo "Checking if iptables MSS Value needs to be updated"
currentMSS=$(iptables -L -t mangle --line-numbers | grep -m 1 'SYN,RST/SYN TCPMSS' | sed 's/.*set \([0-9]\{4\}\).*/\1/')
targetMSS=$(($PTARGET-40))
if [[ $currentMSS -ne $targetMSS ]]; then
echo "Updating MSS from $currentMSS to $targetMSS"
while [[ $(iptables -L -t mangle --line-numbers | grep 'SYN,RST/SYN TCPMSS') ]]; do
iptables -t mangle -D UBIOS_FORWARD_TCPMSS 1
done
iptables -t mangle -A UBIOS_FORWARD_TCPMSS -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss $targetMSS
else
echo "iptables already has correct MSS Value"
fi
fi

if [[ $restartpppd == 1 ]]; then
echo Killing pppd
killall -SIGHUP pppd
Expand Down
15 changes: 15 additions & 0 deletions 11-change-ppp-mtu.sh
100644 → 100755
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@
MINTERFACES="(ppp0)"
# Desired MTU of PPP interfaces
PTARGET=1500
SET_MSS=false

function check_mtu {
ip link list | grep -E $MINTERFACES | grep 'mtu '$PTARGET > /dev/null
Expand Down Expand Up @@ -54,6 +55,20 @@ while true; do
ip link set $pinterface mtu $PTARGET
fi
done

if [[ $SET_MSS ]]; then
echo "Checking if iptables MSS Value needs to be updated"
currentMSS=$(iptables -L -t mangle --line-numbers | grep -m 1 'SYN,RST/SYN TCPMSS' | sed 's/.*set \([0-9]\{4\}\).*/\1/')
targetMSS=$(($PTARGET-40))
if [[ $currentMSS -ne $targetMSS ]]; then
echo "Updating MSS from $currentMSS to $targetMSS"
while [[ $(iptables -L -t mangle --line-numbers | grep 'SYN,RST/SYN TCPMSS') ]]; do
iptables -t mangle -D UBIOS_FORWARD_TCPMSS 1
done
iptables -t mangle -A UBIOS_FORWARD_TCPMSS -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss $targetMSS
fi
fi

# Kill pppd to apply changes (it gets restarted automatically)
# This does take down existing ppp links but as pppd comes straight back up, so should the links
# Only kill pppd if there are ppp interfaces active and changes were made
Expand Down