From fa64a8010d72440412792553ff988fc99e212740 Mon Sep 17 00:00:00 2001
From: Samuel Thibault <samuel.thibault@ens-lyon.org>
Date: Sun, 30 Mar 2025 15:21:21 +0200
Subject: [PATCH] chap: cope with our ack being lost

---
 ppp.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/ppp.c b/ppp.c
index 7a849bd..80ffb17 100644
--- a/ppp.c
+++ b/ppp.c
@@ -207,7 +207,20 @@ void processchap(sessionidt s, tunnelidt t, uint8_t *p, uint16_t l)
 
 	if (session[s].ppp.phase != Authenticate)
 	{
-	    	LOG(2, s, t, "CHAP ignored in %s phase\n", ppp_phase(session[s].ppp.phase));
+		if (session[s].ppp.phase == Network)
+		{
+			uint8_t b[MAXETHER];
+			uint8_t *p2;
+			LOG(2, s, t, "CHAP in Network phase, peer probably missed our ack, confirming it\n");
+			p2 = makeppp(b, sizeof(b), 0, 0, s, t, PPPCHAP, 0, 0, 0);
+			if (!p2) return;
+			*p2 = 3; // ack
+			p2[1] = p[1];
+			*(uint16_t *) (p2 + 2) = ntohs(4); // no message
+			tunnelsend(b, (p2 - b) + 4, t); // send it
+		}
+		else
+			LOG(2, s, t, "CHAP ignored in %s phase\n", ppp_phase(session[s].ppp.phase));
 		return;
 	}