ppp: Request MRU if we ever get NAKed with it

Huawei E160G hardware seems to NAK our configure request and suggest
that it will never send packets bigger than 1440 bytes.  Since we don't
particularly care (our receive ring buffer is 4K, so it can handle 2048
byte packets), we just re-send the Configure Request with the preferred
value.

1 files changed, 45 insertions, 3 deletions

diff --git a/gatchat/ppp_lcp.c b/gatchat/ppp_lcp.c
index 5df29556..7c1ea50f 100644
--- a/gatchat/ppp_lcp.c
+++ b/gatchat/ppp_lcp.c
@@ -58,16 +58,18 @@ enum lcp_options {
 	ACFC			= 8,
 };
 
-/* Maximum size of all options, we only ever request ACCM */ 
-#define MAX_CONFIG_OPTION_SIZE 6
+/* Maximum size of all options, we only ever request ACCM and MRU */ 
+#define MAX_CONFIG_OPTION_SIZE 10
 
-#define REQ_OPTION_ACCM 0x1
+#define REQ_OPTION_ACCM	0x1
+#define REQ_OPTION_MRU	0x2
 
 struct lcp_data {
 	guint8 options[MAX_CONFIG_OPTION_SIZE];
 	guint16 options_len;
 	guint8 req_options;
 	guint32 accm;			/* ACCM value */
+	guint16 mru;
 };
 
 static void lcp_generate_config_options(struct lcp_data *lcp)
@@ -86,6 +88,18 @@ static void lcp_generate_config_options(struct lcp_data *lcp)
 		len += 6;
 	}
 
+	if (lcp->req_options & REQ_OPTION_MRU) {
+		guint16 mru;
+
+		mru = htons(lcp->mru);
+
+		lcp->options[len] = MRU;
+		lcp->options[len + 1] = 4;
+		memcpy(lcp->options + len + 2, &mru, sizeof(mru));
+
+		len += 4;
+	}
+
 	lcp->options_len = len;
 }
 
@@ -146,7 +160,35 @@ static void lcp_rca(struct pppcp_data *pppcp, const struct pppcp_packet *packet)
 static void lcp_rcn_nak(struct pppcp_data *pppcp,
 				const struct pppcp_packet *packet)
 {
+	struct lcp_data *lcp = pppcp_get_data(pppcp);
+	struct ppp_option_iter iter;
 
+	ppp_option_iter_init(&iter, packet);
+
+	while (ppp_option_iter_next(&iter) == TRUE) {
+		const guint8 *data = ppp_option_iter_get_data(&iter);
+
+		switch (ppp_option_iter_get_type(&iter)) {
+		case MRU:
+		{
+			guint16 mru = get_host_short(data);
+
+			if (mru < 2048) {
+				g_print("Setting peer's suggested mru: %hd\n",
+						mru);
+				lcp->mru = get_host_short(data);
+				lcp->req_options |= REQ_OPTION_MRU;
+			}
+
+			break;
+		}
+		default:
+			break;
+		}
+	}
+
+	lcp_generate_config_options(lcp);
+	pppcp_set_local_options(pppcp, lcp->options, lcp->options_len);
 }
 
 static void lcp_rcn_rej(struct pppcp_data *pppcp,