Add a ``Usable'' function to the ccp switch. The function

is called prior to sending a CCP configure request for a
given protocol.  The default is to send the request, but
this is overridden for MPPE which checks to see if the lcp
negotiations agreed CHAP81, and if not fails.

Use the same function to decide if we should reject peer
requests for MPPE.

This should get rid of those boring messages about not being
able to initialise MPPE when we don't negotiate CHAP81.

usr.sbin/ppp/ccp.c

@@ -268,7 +268,8 @@ CcpSendConfigReq(struct fsm *fp)
   ccp->out.algorithm = -1;
   for (f = 0; f < NALGORITHMS; f++)
     if (IsEnabled(ccp->cfg.neg[algorithm[f]->Neg]) &&
-        !REJECTED(ccp, algorithm[f]->id)) {
+        !REJECTED(ccp, algorithm[f]->id) &&
+        (*algorithm[f]->Usable)(fp)) {
 
       if (!alloc)
         for (o = &ccp->out.opt; *o != NULL; o = &(*o)->next)
@@ -491,6 +492,7 @@ CcpDecodeConfig(struct fsm *fp, u_char *cp, int plen, int mode_type,
       switch (mode_type) {
       case MODE_REQ:
 	if (IsAccepted(ccp->cfg.neg[algorithm[f]->Neg]) &&
+            (*algorithm[f]->Usable)(fp) &&
             ccp->in.algorithm == -1) {
 	  memcpy(&ccp->in.opt, cp, length);
           switch ((*algorithm[f]->i.Set)(&ccp->in.opt, &ccp->cfg)) {
@@ -697,4 +699,10 @@ ccp_SetOpenMode(struct ccp *ccp)
   return 0;				/* No CCP at all */
 }
 
+int
+ccp_IsUsable(struct fsm *fp)
+{
+  return 1;
+}
+
 struct layer ccplayer = { LAYER_CCP, "ccp", ccp_LayerPush, ccp_LayerPull };

usr.sbin/ppp/ccp.h

@@ -106,6 +106,7 @@ struct ccp_algorithm {
   int id;
   int Neg;					/* ccp_config neg array item */
   const char *(*Disp)(struct lcp_opt *);	/* Use result immediately !  */
+  int (*Usable)(struct fsm *);			/* Ok to negotiate ? */
   struct {
     int (*Set)(struct lcp_opt *, const struct ccp_config *);
     void *(*Init)(struct lcp_opt *);
@@ -135,5 +136,6 @@ extern int ccp_ReportStatus(struct cmdargs const *);
 extern u_short ccp_Proto(struct ccp *);
 extern void ccp_SetupCallbacks(struct ccp *);
 extern int ccp_SetOpenMode(struct ccp *);
+extern int ccp_IsUsable(struct fsm *);
 
 extern struct layer ccplayer;

usr.sbin/ppp/deflate.c

@@ -551,9 +551,10 @@ DeflateTermOutput(void *v)
 }
 
 const struct ccp_algorithm PppdDeflateAlgorithm = {
-  TY_PPPD_DEFLATE,	/* pppd (wrongly) expects this ``type'' field */
+  TY_PPPD_DEFLATE,	/* Older versions of pppd expected this ``type'' */
   CCP_NEG_DEFLATE24,
   DeflateDispOpts,
+  ccp_IsUsable,
   {
     DeflateSetOptsInput,
     DeflateInitInput,
@@ -576,6 +577,7 @@ const struct ccp_algorithm DeflateAlgorithm = {
   TY_DEFLATE,		/* rfc 1979 */
   CCP_NEG_DEFLATE,
   DeflateDispOpts,
+  ccp_IsUsable,
   {
     DeflateSetOptsInput,
     DeflateInitInput,

usr.sbin/ppp/mppe.c

@@ -47,7 +47,11 @@
 #include "hdlc.h"
 #include "lcp.h"
 #include "ccp.h"
+#include "throughput.h"
+#include "layer.h"
+#include "link.h"
 #include "chap_ms.h"
+#include "proto.h"
 #include "mppe.h"
 
 /*
@@ -223,6 +227,21 @@ MPPEDispOpts(struct lcp_opt *o)
   return buf;
 }
 
+static int
+MPPEUsable(struct fsm *fp)
+{
+  struct lcp *lcp;
+  int ok;
+
+  lcp = &fp->link->lcp;
+  ok = (lcp->want_auth == PROTO_CHAP && lcp->want_authtype == 0x81) ||
+       (lcp->his_auth == PROTO_CHAP && lcp->his_authtype == 0x81);
+  if (!ok)
+    log_Printf(LogCCP, "MPPE: Not usable without CHAP81\n");
+
+  return ok;
+}
+
 static void
 MPPEInitOptsOutput(struct lcp_opt *o, const struct ccp_config *cfg)
 {
@@ -414,6 +433,7 @@ const struct ccp_algorithm MPPEAlgorithm = {
   TY_MPPE,
   CCP_NEG_MPPE,
   MPPEDispOpts,
+  MPPEUsable,
   {
     MPPESetOptsInput,
     MPPEInitInput,

usr.sbin/ppp/pred.c

@@ -323,6 +323,7 @@ const struct ccp_algorithm Pred1Algorithm = {
   TY_PRED1,
   CCP_NEG_PRED1,
   Pred1DispOpts,
+  ccp_IsUsable,
   {
     Pred1SetOptsInput,
     Pred1InitInput,