Add support for LZS decompression in DTLS

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

cstp.c

@@ -218,9 +218,11 @@ static int start_cstp_connection(struct openconnect_info *vpninfo)
 			     _("CRITICAL ERROR: DTLS master secret is uninitialised. Please report this.\n"));
 		return -EINVAL;
 	}
-
-	buf_append(reqbuf, "\r\nX-DTLS-CipherSuite: %s\r\n\r\n",
+	buf_append(reqbuf, "\r\nX-DTLS-CipherSuite: %s\r\n",
 			       vpninfo->dtls_ciphers ? : DEFAULT_CIPHER_LIST);
+	if (vpninfo->req_compr & COMPR_LZS)
+		buf_append(reqbuf, "X-DTLS-Accept-Encoding: lzs\r\n");
+	buf_append(reqbuf, "\r\n");
 
 	if (buf_error(reqbuf)) {
 		vpn_progress(vpninfo, PRG_ERR,
@@ -353,6 +355,15 @@ static int start_cstp_connection(struct openconnect_info *vpninfo)
 
 				if (dtls_sessid_changed && vpninfo->dtls_state > DTLS_SLEEPING)
 					vpninfo->dtls_need_reconnect = 1;
+			} else if (!strcmp(buf + 7, "Content-Encoding")) {
+				if (!strcmp(colon, "lzs"))
+					vpninfo->dtls_compr = COMPR_LZS;
+				else {
+					vpn_progress(vpninfo, PRG_ERR,
+						     _("Unknown DTLS-Content-Encoding %s\n"),
+						     colon);
+					return -EINVAL;
+				}
 			}
 			continue;
 		}
@@ -663,7 +674,7 @@ static int cstp_reconnect(struct openconnect_info *vpninfo)
 	return 0;
 }
 
-static int decompress_and_queue_packet(struct openconnect_info *vpninfo,
+int decompress_and_queue_packet(struct openconnect_info *vpninfo,
 				unsigned char *buf, int len)
 {
 	struct pkt *new = malloc(sizeof(struct pkt) + vpninfo->ip_info.mtu);

dtls.c

@@ -754,6 +754,15 @@ int dtls_mainloop(struct openconnect_info *vpninfo, int *timeout)
 			vpn_progress(vpninfo, PRG_DEBUG, _("Got DTLS Keepalive\n"));
 			break;
 
+		case AC_PKT_COMPRESSED:
+			if (!vpninfo->dtls_compr) {
+				vpn_progress(vpninfo, PRG_ERR,
+					     _("Compressed DTLS packet received when compression not enabled\n"));
+				goto unknown_pkt;
+			}
+			decompress_and_queue_packet(vpninfo, vpninfo->dtls_pkt->data,
+						    len - 1);
+			break;
 		default:
 			vpn_progress(vpninfo, PRG_ERR,
 				     _("Unknown DTLS packet type %02x, len %d\n"),
@@ -766,6 +775,7 @@ int dtls_mainloop(struct openconnect_info *vpninfo, int *timeout)
 				 * the appropriate length of garbage. So don't abort... for now. */
 				break;
 			} else {
+			unknown_pkt:
 				vpninfo->quit_reason = "Unknown packet received";
 				return 1;
 			}

openconnect-internal.h

@@ -631,6 +631,8 @@ void dtls_shutdown(struct openconnect_info *vpninfo);
 int cstp_mainloop(struct openconnect_info *vpninfo, int *timeout);
 int cstp_bye(struct openconnect_info *vpninfo, const char *reason);
 void cstp_free_splits(struct openconnect_info *vpninfo);
+int decompress_and_queue_packet(struct openconnect_info *vpninfo,
+				unsigned char *buf, int len);
 
 /* lzs.c */
 int lzs_decompress(unsigned char *dst, int dstlen, const unsigned char *src, int srclen);