Reduce the interface MTU by 2 when MPPE has been successfully negotiated.

This is necessary because MPPE will combine the protocol id with the
payload received on the tun interface, encrypt it, then prepend its
own protocol id, effectively increasing the payload by two bytes.

1 files changed, 1 insertions, 0 deletions

diff --git a/usr.sbin/ppp/pred.c b/usr.sbin/ppp/pred.c
index 47d9a8c..d1a5b53 100644
--- a/usr.sbin/ppp/pred.c
+++ b/usr.sbin/ppp/pred.c
@@ -340,6 +340,7 @@ const struct ccp_algorithm Pred1Algorithm = {
     Pred1DictSetup
   },
   {
+    0,
     Pred1InitOptsOutput,
     Pred1SetOptsOutput,
     Pred1InitOutput,