From dfffe4b963d96404ab9fb04bb172ad60d370e6ef Mon Sep 17 00:00:00 2001
From: Ruslan Mstoi <ruslan.mstoi@intel.com>
Date: Mon, 24 Apr 2017 16:10:52 +0300
Subject: [PATCH] drivers: slip: escape SLIP special characters in headers too

Otherwise they are send as is and stripped by tunslip6, resulting in
malformed packets.

Jira: ZEP-2037

Change-Id: I1267b9ac956f3cd7aa3456ce20447ef97281d7a8
Signed-off-by: Ruslan Mstoi <ruslan.mstoi@intel.com>
---
 drivers/slip/slip.c | 57 ++++++++++++++++++++++++++-------------------
 1 file changed, 33 insertions(+), 24 deletions(-)

diff --git a/drivers/slip/slip.c b/drivers/slip/slip.c
index fdd2d8cfd61..52c277b19e4 100644
--- a/drivers/slip/slip.c
+++ b/drivers/slip/slip.c
@@ -125,6 +125,37 @@ static inline void slip_writeb(unsigned char c)
 	uart_pipe_send(&buf[0], 1);
 }
 
+/**
+ *  @brief Write byte to SLIP, escape if it is END or ESC character
+ *
+ *  @param c  a byte to write
+ */
+static void slip_writeb_esc(unsigned char c)
+{
+	switch (c) {
+	case SLIP_END:
+		/* If it's the same code as an END character,
+		 * we send a special two character code so as
+		 * not to make the receiver think we sent
+		 * an END.
+		 */
+		slip_writeb(SLIP_ESC);
+		slip_writeb(SLIP_ESC_END);
+		break;
+	case SLIP_ESC:
+		/* If it's the same code as an ESC character,
+		 * we send a special two character code so as
+		 * not to make the receiver think we sent
+		 * an ESC.
+		 */
+		slip_writeb(SLIP_ESC);
+		slip_writeb(SLIP_ESC_ESC);
+		break;
+	default:
+		slip_writeb(c);
+	}
+}
+
 static int slip_send(struct net_if *iface, struct net_pkt *pkt)
 {
 	struct net_buf *frag;
@@ -154,7 +185,7 @@ static int slip_send(struct net_if *iface, struct net_pkt *pkt)
 		/* This writes ethernet header */
 		if (!send_header_once && ll_reserve) {
 			for (i = 0; i < ll_reserve; i++) {
-				slip_writeb(*ptr++);
+				slip_writeb_esc(*ptr++);
 			}
 		}
 
@@ -174,29 +205,7 @@ static int slip_send(struct net_if *iface, struct net_pkt *pkt)
 
 		for (i = 0; i < frag->len; ++i) {
 			c = *ptr++;
-
-			switch (c) {
-			case SLIP_END:
-				/* If it's the same code as an END character,
-				 * we send a special two character code so as
-				 * not to make the receiver think we sent
-				 * an END.
-				 */
-				slip_writeb(SLIP_ESC);
-				slip_writeb(SLIP_ESC_END);
-				break;
-			case SLIP_ESC:
-				/* If it's the same code as an ESC character,
-				 * we send a special two character code so as
-				 * not to make the receiver think we sent
-				 * an ESC.
-				 */
-				slip_writeb(SLIP_ESC);
-				slip_writeb(SLIP_ESC_ESC);
-				break;
-			default:
-				slip_writeb(c);
-			}
+			slip_writeb_esc(c);
 		}
 
 #if defined(CONFIG_SLIP_DEBUG)