From: Daniel Lenski <dlenski@gmail.com>
Date: Tue, 19 May 2020 17:54:22 +0000 (-0700)
Subject: add standard-based PPP framing (RFC1661, RFC1662) as reference points
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=d774e57e13bbe14e773e4518a2575118f6559418;p=users%2Fdwmw2%2Fopenconnect.git

add standard-based PPP framing (RFC1661, RFC1662) as reference points

- PPP_ENCAP_RFC1661: Plain PPP. “Synchronous” in the ’90s-era language,
  because the start and end of the frame are known from external means.

  In modern instances, this is because they arrive in a complete packet with
  a known length from its lower-level encapsulation. (TLS or DTLS records in
  our expected use cases.)

  This is what `pppd sync` does.

- PPP_ENCAP_RFC1662: “PPP in HDLC-like framing.”

  This is what `pppd` without `sync` does.

At some point, we will be able to add automated testing of our PPP
implementation's ability to communicate with `pppd`.

Signed-off-by: Daniel Lenski <dlenski@gmail.com>
---

diff --git a/openconnect-internal.h b/openconnect-internal.h
index 4b00da59..4e88f91c 100644
--- a/openconnect-internal.h
+++ b/openconnect-internal.h
@@ -176,10 +176,12 @@ struct pkt {
 #define DTLS_CONNECTING	4	/* ESP probe received; must tell server */
 #define DTLS_CONNECTED	5	/* Server informed and should be sending ESP */
 
-#define PPP_ENCAP_F5		1	/* F5 BigIP no HDLC */
-#define PPP_ENCAP_F5_HDLC	2	/* F5 BigIP HDLC */
-#define PPP_ENCAP_FORTINET_HDLC	3	/* Fortinet HDLC */
-#define PPP_ENCAP_NX_HDLC	4	/* SonicWall NetExtender HDLC */
+#define PPP_ENCAP_RFC1661	1	/* Plain/synchronous/pre-framed PPP (RFC1661) */
+#define PPP_ENCAP_RFC1662_HDLC	2	/* PPP with HDLC-like framing (RFC1662) */
+#define PPP_ENCAP_F5		3	/* F5 BigIP no HDLC */
+#define PPP_ENCAP_F5_HDLC	4	/* F5 BigIP HDLC */
+#define PPP_ENCAP_FORTINET_HDLC	5	/* Fortinet HDLC */
+#define PPP_ENCAP_NX_HDLC	6	/* SonicWall NetExtender HDLC */
 #define PPP_ENCAP_MAX		PPP_ENCAP_NX_HDLC
 
 #define COMPR_DEFLATE	(1<<0)
diff --git a/ppp.c b/ppp.c
index d5164b26..2faa49ff 100644
--- a/ppp.c
+++ b/ppp.c
@@ -168,6 +168,8 @@ static const char *ppps_names[] = {
 
 static const char *encap_names[PPP_ENCAP_MAX+1] = {
 	NULL,
+	"RFC1661",
+	"RFC1662 HDLC",
 	"F5",
 	"F5 HDLC",
 	"FORTINET HDLC",
@@ -242,6 +244,7 @@ int openconnect_ppp_new(struct openconnect_info *vpninfo,
 
 	case PPP_ENCAP_F5_HDLC:
 	case PPP_ENCAP_FORTINET_HDLC:
+	case PPP_ENCAP_RFC1662_HDLC:
 		ppp->encap_len = 0;
 		ppp->hdlc = 1;
 		break;
@@ -251,6 +254,10 @@ int openconnect_ppp_new(struct openconnect_info *vpninfo,
 		ppp->hdlc = 1;
 		break;
 
+	case PPP_ENCAP_RFC1661:
+		ppp->encap_len = 0;
+		break;
+
 	default:
 		free(ppp);
 		return -EINVAL;
@@ -989,7 +996,7 @@ int ppp_mainloop(struct openconnect_info *vpninfo, int *timeout, int readable)
 		if (vpninfo->dump_http_traffic)
 			dump_buf_hex(vpninfo, PRG_DEBUG, '<', eh, len);
 
-		/* check pre-PPP header */
+		/* Deencapsulate from pre-PPP header */
 		switch (ppp->encap) {
 		case PPP_ENCAP_F5:
 			magic = load_be16(eh);
@@ -1022,6 +1029,7 @@ int ppp_mainloop(struct openconnect_info *vpninfo, int *timeout, int readable)
 
 		case PPP_ENCAP_F5_HDLC:
 		case PPP_ENCAP_FORTINET_HDLC:
+		case PPP_ENCAP_RFC1662_HDLC:
 			payload_len = unhdlc_in_place(vpninfo, eh + ppp->encap_len, len - ppp->encap_len, &next);
 			if (payload_len < 0)
 				continue; /* unhdlc_in_place already logged */
@@ -1033,6 +1041,11 @@ int ppp_mainloop(struct openconnect_info *vpninfo, int *timeout, int readable)
 			vpn_progress(vpninfo, PRG_ERR, _("Invalid PPP encapsulation\n"));
 			vpninfo->quit_reason = "Invalid encapsulation";
 			return -EINVAL;
+
+		case PPP_ENCAP_RFC1661:
+			payload_len = len;
+			next = eh + payload_len;
+			break;
 		}
 
 		ph = eh + ppp->encap_len;
@@ -1259,7 +1272,7 @@ int ppp_mainloop(struct openconnect_info *vpninfo, int *timeout, int readable)
 			vpninfo->current_ssl_pkt = this;
 		}
 
-		/* Add pre-PPP encapsulation header */
+		/* Encapsulate into pre-PPP header */
 		eh = this->data - this->ppp.hlen - ppp->encap_len;
 		switch (ppp->encap) {
 		case PPP_ENCAP_F5: