From 8e50756afa04b5aec5e9346609932ca9c23830c9 Mon Sep 17 00:00:00 2001
From: Santiago Alessandri <san.lt.ss@gmail.com>
Date: Sat, 4 Nov 2017 12:08:34 -0700
Subject: [PATCH] Add MPLS experimental field (#265)

* Add experimental field to MPLS PDU

See RFC-4950 https://tools.ietf.org/html/rfc4950

* Add tests for MPLS' experimental field
---
 include/tins/mpls.h     | 24 +++++++++++++++++++-----
 src/mpls.cpp            |  8 ++++++--
 tests/src/mpls_test.cpp | 11 ++++++++++-
 3 files changed, 35 insertions(+), 8 deletions(-)

diff --git a/include/tins/mpls.h b/include/tins/mpls.h
index d13dafc..150a2dd 100644
--- a/include/tins/mpls.h
+++ b/include/tins/mpls.h
@@ -73,15 +73,22 @@ public:
      * \brief Getter for the label field.
      */
     small_uint<20> label() const {
-        return (Endian::be_to_host(header_.label_high) << 4) | 
-               ((header_.label_low_and_bottom >> 4) & 0xf);
+        return (Endian::be_to_host(header_.label_high) << 4) |
+               ((header_.label_low_exp_and_bottom >> 4) & 0xf);
+    }
+
+    /**
+     * \brief Getter for the experimental field.
+     */
+    small_uint<3> experimental() const {
+        return (header_.label_low_exp_and_bottom >> 1) & 0x7;
     }
 
     /**
      * \brief Getter for the bottom of the stack field.
      */
     small_uint<1> bottom_of_stack() const {
-        return header_.label_low_and_bottom & 0x1;
+        return header_.label_low_exp_and_bottom & 0x1;
     }
 
     /**
@@ -98,11 +105,18 @@ public:
      */
     void label(small_uint<20> value);
 
+    /**
+     * \brief Setter for the experimental field
+     *
+     * \param value The new experimental field value
+     */
+    void experimental(small_uint<3> value);
+
     /**
      * \brief Setter for the bottom of the stack field
      *
      * Note that if this MPLS layer is somewhere between an Ethernet and IP
-     * layers, the bottom of the stack field will be overriden and set 
+     * layers, the bottom of the stack field will be overriden and set
      * automatically. You should only set this field when constructing ICMP
      * extensions.
      *
@@ -143,7 +157,7 @@ private:
     TINS_BEGIN_PACK
     struct mpls_header {
         uint16_t label_high;
-        uint8_t label_low_and_bottom;
+        uint8_t label_low_exp_and_bottom;
         uint8_t ttl;
     } TINS_END_PACK;
 
diff --git a/src/mpls.cpp b/src/mpls.cpp
index 58e341c..c43860f 100644
--- a/src/mpls.cpp
+++ b/src/mpls.cpp
@@ -76,11 +76,15 @@ void MPLS::label(small_uint<20> value) {
     const uint16_t label_high = Endian::host_to_be<uint16_t>(label_value >> 4);
     const uint8_t label_low = (label_value << 4) & 0xf0;
     header_.label_high = label_high & 0xffff;
-    header_.label_low_and_bottom = (header_.label_low_and_bottom & 0x0f) | label_low;
+    header_.label_low_exp_and_bottom = (header_.label_low_exp_and_bottom & 0x0f) | label_low;
+}
+
+void MPLS::experimental(small_uint<3> value) {
+    header_.label_low_exp_and_bottom = (header_.label_low_exp_and_bottom & 0xf1) | (value << 1);
 }
 
 void MPLS::bottom_of_stack(small_uint<1> value) {
-    header_.label_low_and_bottom = (header_.label_low_and_bottom & 0xfe) | value;
+    header_.label_low_exp_and_bottom = (header_.label_low_exp_and_bottom & 0xfe) | value;
 }
 
 void MPLS::ttl(uint8_t value) {
diff --git a/tests/src/mpls_test.cpp b/tests/src/mpls_test.cpp
index 8fd5dac..6535e3c 100644
--- a/tests/src/mpls_test.cpp
+++ b/tests/src/mpls_test.cpp
@@ -26,7 +26,7 @@ const uint8_t MPLSTest::eth_and_mpls[] = {
 };
 
 const uint8_t MPLSTest::mpls_layer[] = {
-    24, 150, 1, 1
+    24, 150, 3, 1
 };
 
 TEST_F(MPLSTest, ConstructWholePacket) {
@@ -63,6 +63,7 @@ TEST_F(MPLSTest, ConstructWholePacket) {
 TEST_F(MPLSTest, ConstructorFromBuffer) {
     MPLS mpls(mpls_layer, sizeof(mpls_layer));
     EXPECT_EQ(100704U, mpls.label());
+    EXPECT_EQ(1, mpls.experimental());
     EXPECT_EQ(1, mpls.bottom_of_stack());
     EXPECT_EQ(1, mpls.ttl());
 }
@@ -100,9 +101,11 @@ TEST_F(MPLSTest, SetAllFields) {
     mpls.ttl(0xde);
     mpls.bottom_of_stack(1);
     mpls.label(0xdead8);
+    mpls.experimental(6);
     EXPECT_EQ(0xdead8U, mpls.label());
     EXPECT_EQ(1, mpls.bottom_of_stack());
     EXPECT_EQ(0xde, mpls.ttl());
+    EXPECT_EQ(6, mpls.experimental());
 }
 
 TEST_F(MPLSTest, Label) {
@@ -111,6 +114,12 @@ TEST_F(MPLSTest, Label) {
     EXPECT_EQ(0xdead8U, mpls.label());
 }
 
+TEST_F(MPLSTest, Experimental) {
+    MPLS mpls;
+    mpls.experimental(4);
+    EXPECT_EQ(4, mpls.experimental());
+}
+
 TEST_F(MPLSTest, BottomOfStack) {
     MPLS mpls;
     mpls.bottom_of_stack(1);