+ if ((go->neg_chap || go->neg_upap)
+ && len >= CILEN_SHORT
+ && p[0] == CI_AUTHTYPE && p[1] >= CILEN_SHORT && p[1] <= len) {
+ cilen = p[1];
+ len -= cilen;
+ no.neg_chap = go->neg_chap;
+ no.neg_upap = go->neg_upap;
+ INCPTR(2, p);
+ GETSHORT(cishort, p);
+ if (cishort == PPP_PAP && cilen == CILEN_SHORT) {
+ /*
+ * If we were asking for CHAP, they obviously don't want to do it.
+ * If we weren't asking for CHAP, then we were asking for PAP,
+ * in which case this Nak is bad.
+ */
+ if (!go->neg_chap)
+ goto bad;
+ try.neg_chap = 0;
+
+ } else if (cishort == PPP_CHAP && cilen == CILEN_CHAP) {
+ GETCHAR(cichar, p);
+ if (go->neg_chap) {
+ /*
+ * We were asking for CHAP/MD5; they must want a different
+ * algorithm. If they can't do MD5, we'll have to stop
+ * asking for CHAP.
+ */
+ if (cichar != go->chap_mdtype)
+ try.neg_chap = 0;
+ } else {
+ /*
+ * Stop asking for PAP if we were asking for it.
+ */
+ try.neg_upap = 0;
+ }
+
+ } else {
+ /*
+ * We don't recognize what they're suggesting.
+ * Stop asking for what we were asking for.
+ */
+ if (go->neg_chap)
+ try.neg_chap = 0;
+ else
+ try.neg_upap = 0;
+ p += cilen - CILEN_SHORT;
+ }