When the peer fails to specify an MRU and a 1500 byte MRU is not

allowed either because of the transport or configuration, send a
MRU NAK only once, then allow the negotiations to proceed.

rfc1661 says that 1500 should always be allowed and rfc2516 says
that 1492 is the maximum for PPPoE.  This changes ppp so that it
only weakly suggests 1492, then goes with the default (leaving
the problem in the hands of the peer WRT how they set their MTU).

MFC after: 1 week

1 files changed, 7 insertions, 4 deletions

diff --git a/usr.sbin/ppp/lcp.c b/usr.sbin/ppp/lcp.c
index 4b9dfd9..e75ee72 100644
--- a/usr.sbin/ppp/lcp.c
+++ b/usr.sbin/ppp/lcp.c
@@ -297,6 +297,7 @@ lcp_Setup(struct lcp *lcp, int openmode)
   lcp->his_authtype = 0;
   lcp->his_callback.opmask = 0;
   lcp->his_shortseq = 0;
+  lcp->mru_req = 0;
 
   if ((lcp->want_mru = lcp->cfg.mru) == 0)
     lcp->want_mru = DEF_MRU;
@@ -554,6 +555,7 @@ LcpLayerStart(struct fsm *fp)
   log_Printf(LogLCP, "%s: LayerStart\n", fp->link->name);
   lcp->LcpFailedMagic = 0;
   fp->more.reqs = fp->more.naks = fp->more.rejs = lcp->cfg.fsm.maxreq * 3;
+  lcp->mru_req = 0;
 }
 
 static void
@@ -618,7 +620,7 @@ LcpDecodeConfig(struct fsm *fp, u_char *cp, int plen, int mode_type,
 {
   /* Deal with incoming PROTO_LCP */
   struct lcp *lcp = fsm2lcp(fp);
-  int type, length, sz, pos, op, callback_req, mru_req;
+  int type, length, sz, pos, op, callback_req;
   u_int32_t magic, accmap;
   u_short mru, phmtu, maxmtu, maxmru, wantmtu, wantmru, proto;
   struct lqrreq *req;
@@ -626,7 +628,7 @@ LcpDecodeConfig(struct fsm *fp, u_char *cp, int plen, int mode_type,
   struct mp *mp;
   struct physical *p = link2physical(fp->link);
 
-  sz = op = callback_req = mru_req = 0;
+  sz = op = callback_req = 0;
 
   while (plen >= sizeof(struct fsmconfig)) {
     type = *cp;
@@ -696,7 +698,7 @@ LcpDecodeConfig(struct fsm *fp, u_char *cp, int plen, int mode_type,
       break;
 
     case TY_MRU:
-      mru_req = 1;
+      lcp->mru_req = 1;
       ua_ntohs(cp + 2, &mru);
       log_Printf(LogLCP, "%s %d\n", request, mru);
 
@@ -1274,7 +1276,7 @@ reqreject:
         dec->nakend[-1] = 2;	/* XXX: Silly ! */
       }
     }
-    if (mode_type == MODE_REQ && !mru_req) {
+    if (mode_type == MODE_REQ && !lcp->mru_req) {
       mru = DEF_MRU;
       phmtu = p ? physical_DeviceMTU(p) : 0;
       if (phmtu && mru > phmtu)
@@ -1288,6 +1290,7 @@ reqreject:
         *dec->nakend++ = 4;
         ua_htons(&lcp->his_mru, dec->nakend);
         dec->nakend += 2;
+        lcp->mru_req = 1;	/* Don't keep NAK'ing this */
       }
     }
     if (dec->rejend != dec->rej) {