Early development stage of an attempt to port PPPd 2.4.5 to lwIP.

PPPoE works, PPPoS code is not ported at all.

I am using the RP-PPPoE server to do my tests using the following
configuration:

$ cat /etc/ppp/pppoe-server-options
debug
login
lcp-echo-interval 10
lcp-echo-failure 10
ms-dns 192.168.4.130
ms-dns 192.168.4.231
netmask 255.255.255.0
defaultroute
noipdefault
usepeerdns

$ cat /etc/ppp/allip
192.168.4.1-200

$ pppoe-server -C isp -L 192.168.4.254 -p /etc/ppp/allip -I tap0

Plus the usual auth-lines in /etc/ppp/pap-secrets and
/etc/ppp/chap-secrets .

And the unix port minimal "echo" project slightly modified to use
the "tcpip" API, so with threads, which I am going to commit with
NO_SYS as a -Dmacro.

It still use some of the linux'ism, such as syslog() and crypt(),

I do not want to drop the syslog() supports at the moment, this is
pretty useful to debug, and we may just convert the way the syslog() is
done to provide a trace feature to our PPP users, as a compile-time
option.

src/netif/ppp/chap-new.h

@@ -0,0 +1,130 @@
+/*
+ * chap-new.c - New CHAP implementation.
+ *
+ * Copyright (c) 2003 Paul Mackerras. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. The name(s) of the authors of this software must not be used to
+ *    endorse or promote products derived from this software without
+ *    prior written permission.
+ *
+ * 3. Redistributions of any form whatsoever must retain the following
+ *    acknowledgment:
+ *    "This product includes software developed by Paul Mackerras
+ *     <paulus@samba.org>".
+ *
+ * THE AUTHORS OF THIS SOFTWARE DISCLAIM ALL WARRANTIES WITH REGARD TO
+ * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS, IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
+ * SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
+ * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
+ * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/*
+ * CHAP packets begin with a standard header with code, id, len (2 bytes).
+ */
+#define CHAP_HDRLEN	4
+
+/*
+ * Values for the code field.
+ */
+#define CHAP_CHALLENGE	1
+#define CHAP_RESPONSE	2
+#define CHAP_SUCCESS	3
+#define CHAP_FAILURE	4
+
+/*
+ * CHAP digest codes.
+ */
+#define CHAP_MD5		5
+#define CHAP_MICROSOFT		0x80
+#define CHAP_MICROSOFT_V2	0x81
+
+/*
+ * Semi-arbitrary limits on challenge and response fields.
+ */
+#define MAX_CHALLENGE_LEN	64
+#define MAX_RESPONSE_LEN	64
+
+/* bitmask of supported algorithms */
+#define MDTYPE_MICROSOFT_V2	0x1
+#define MDTYPE_MICROSOFT	0x2
+#define MDTYPE_MD5		0x4
+#define MDTYPE_NONE		0
+
+/* hashes supported by this instance of pppd */
+extern int chap_mdtype_all;
+
+/* Return the digest alg. ID for the most preferred digest type. */
+#define CHAP_DIGEST(mdtype) \
+    ((mdtype) & MDTYPE_MD5)? CHAP_MD5: \
+    ((mdtype) & MDTYPE_MICROSOFT_V2)? CHAP_MICROSOFT_V2: \
+    ((mdtype) & MDTYPE_MICROSOFT)? CHAP_MICROSOFT: \
+    0
+
+/* Return the bit flag (lsb set) for our most preferred digest type. */
+#define CHAP_MDTYPE(mdtype) ((mdtype) ^ ((mdtype) - 1)) & (mdtype)
+
+/* Return the bit flag for a given digest algorithm ID. */
+#define CHAP_MDTYPE_D(digest) \
+    ((digest) == CHAP_MICROSOFT_V2)? MDTYPE_MICROSOFT_V2: \
+    ((digest) == CHAP_MICROSOFT)? MDTYPE_MICROSOFT: \
+    ((digest) == CHAP_MD5)? MDTYPE_MD5: \
+    0
+
+/* Can we do the requested digest? */
+#define CHAP_CANDIGEST(mdtype, digest) \
+    ((digest) == CHAP_MICROSOFT_V2)? (mdtype) & MDTYPE_MICROSOFT_V2: \
+    ((digest) == CHAP_MICROSOFT)? (mdtype) & MDTYPE_MICROSOFT: \
+    ((digest) == CHAP_MD5)? (mdtype) & MDTYPE_MD5: \
+    0
+
+/*
+ * The code for each digest type has to supply one of these.
+ */
+struct chap_digest_type {
+	int code;
+
+	/*
+	 * Note: challenge and response arguments below are formatted as
+	 * a length byte followed by the actual challenge/response data.
+	 */
+	void (*generate_challenge)(unsigned char *challenge);
+	int (*verify_response)(int id, char *name,
+		unsigned char *secret, int secret_len,
+		unsigned char *challenge, unsigned char *response,
+		char *message, int message_space);
+	void (*make_response)(unsigned char *response, int id, char *our_name,
+		unsigned char *challenge, char *secret, int secret_len,
+		unsigned char *priv);
+	int (*check_success)(unsigned char *pkt, int len, unsigned char *priv);
+	void (*handle_failure)(unsigned char *pkt, int len);
+
+	struct chap_digest_type *next;
+};
+
+/* Hook for a plugin to validate CHAP challenge */
+extern int (*chap_verify_hook)(char *name, char *ourname, int id,
+			struct chap_digest_type *digest,
+			unsigned char *challenge, unsigned char *response,
+			char *message, int message_space);
+
+/* Called by digest code to register a digest type */
+extern void chap_register_digest(struct chap_digest_type *);
+
+/* Called by authentication code to start authenticating the peer. */
+extern void chap_auth_peer(int unit, char *our_name, int digest_code);
+
+/* Called by auth. code to start authenticating us to the peer. */
+extern void chap_auth_with_peer(int unit, char *our_name, int digest_code);
+
+/* Represents the CHAP protocol to the main pppd code */
+extern struct protent chap_protent;