[80211ac] Add partial beamforming support

Adds support to decode beamforming report, but actual beamforming
matrices are not decoded. Requires bit level manipulation of varying lengths
of data which is not currently supported, and section spec only seems to
mention size and contents, not representation

Bug 10169
Change-Id: Icc2188b79f95b5e38b64ded348b7a0696b5504ed
Reviewed-on: https://code.wireshark.org/review/7111
Reviewed-by: Michael Mann <mmann78@netscape.net>
Reviewed-by: Alexis La Goutte <alexis.lagoutte@gmail.com>

1 files changed, 260 insertions, 5 deletions

diff --git a/epan/dissectors/packet-ieee80211.c b/epan/dissectors/packet-ieee80211.c
index c90856c5a0..0f478e7f1f 100644
--- a/epan/dissectors/packet-ieee80211.c
+++ b/epan/dissectors/packet-ieee80211.c
@@ -247,6 +247,20 @@ typedef struct mimo_control
   guint8 remaining_matrix_segment;
 } mimo_control_t;
 
+typedef struct vht_mimo_control
+{
+  guint8 nc;
+  guint8 nr;
+  guint8 chan_width;
+  guint8 grouping;
+  gboolean codebook_info;
+  gboolean feedback_type;
+  guint8 remaining_feedback_segment;
+  gboolean first_feedback_segment;
+  guint8 reserved;
+  guint8 token;
+} vht_mimo_control_t;
+
 /* ************************************************************************* */
 /*                          Miscellaneous Constants                          */
 /* ************************************************************************* */
@@ -4218,6 +4232,8 @@ static int hf_ieee80211_ff_vht_mimo_cntrl_first_feedback_seg = -1;
 static int hf_ieee80211_ff_vht_mimo_cntrl_reserved = -1;
 static int hf_ieee80211_ff_vht_mimo_cntrl_sounding_dialog_token_number = -1;
 static int hf_ieee80211_vht_compressed_beamforming_report = -1;
+static int hf_ieee80211_vht_compressed_beamforming_report_snr = -1;
+static int hf_ieee80211_vht_compressed_beamforming_feedback_matrix = -1;
 static int hf_ieee80211_vht_group_id_management = -1;
 static int hf_ieee80211_vht_operation_mode_notification = -1;
 
@@ -5070,6 +5086,9 @@ static gint ett_vht_ndp_annc_token_tree = -1;
 static gint ett_vht_ndp_annc_sta_info_tree = -1;
 
 static gint ett_ff_vhtmimo_cntrl = -1;
+static gint ett_ff_vhtmimo_beamforming_report = -1;
+static gint ett_ff_vhtmimo_beamforming_report_snr = -1;
+static gint ett_ff_vhtmimo_beamforming_report_feedback_matrices = -1;
 
 static gint ett_ht_info_delimiter1_tree = -1;
 static gint ett_ht_info_delimiter2_tree = -1;
@@ -9069,10 +9088,11 @@ add_ff_action_unprotected_dmg(proto_tree *tree, tvbuff_t *tvb, packet_info *pinf
 }
 
 static guint
-add_ff_vht_mimo_cntrl(proto_tree *tree, tvbuff_t *tvb, packet_info *pinfo _U_, int offset)
+add_ff_vht_mimo_cntrl(proto_tree *tree, tvbuff_t *tvb, packet_info *pinfo _U_, int offset, vht_mimo_control_t *cntrl)
 {
   proto_item *vht_mimo_item;
   proto_tree *vht_mimo_tree;
+  guint32 vht_mimo;
 
   vht_mimo_item = proto_tree_add_item(tree, hf_ieee80211_ff_vht_mimo_cntrl, tvb,
                                   offset, 3, ENC_NA);
@@ -9099,15 +9119,239 @@ add_ff_vht_mimo_cntrl(proto_tree *tree, tvbuff_t *tvb, packet_info *pinfo _U_, i
   proto_tree_add_item(vht_mimo_tree, hf_ieee80211_ff_vht_mimo_cntrl_sounding_dialog_token_number, tvb,
                       offset, 3, ENC_LITTLE_ENDIAN);
 
+  /* Fill vht_mimo_control_t for beamforming use */
+  vht_mimo = tvb_get_letoh24(tvb, offset);
+  cntrl->nc = (vht_mimo & 0x7) + 1;
+  cntrl->nr = ((vht_mimo & 0x38) >> 3) + 1;
+  cntrl->chan_width = (vht_mimo & 0xC0) >> 6;
+  cntrl->grouping = ((vht_mimo & 0x300) >> 8);
+  cntrl->codebook_info = (vht_mimo & 0x400) >> 10;
+  cntrl->feedback_type = (vht_mimo & 0x800) >> 11;
+  cntrl->remaining_feedback_segment = (vht_mimo & 0x7000) >> 12;
+  cntrl->first_feedback_segment = (vht_mimo & 0x8000) >> 15;
+  cntrl->reserved = (vht_mimo & 0x30000) >> 16;
+  cntrl->token = (vht_mimo & 0xfc0000) >> 18;
   return 3;
 }
 
+/* There is no easy way to skip all these subcarrier indices that must not
+ * be displayed when showing compressed beamforming feedback matrices
+ * Table 8-53g IEEE Std 802.11ac-2013 amendment.
+ *
+ * The irregular use of case statements in this function is to improve
+ * readability in what is otherwise a large funtion that does very little.
+ */
+static inline int vht_compressed_skip_scidx(guint8 nchan_width, guint8 ng, int scidx)
+{
+  switch(nchan_width) {
+    /* 20 MHz */
+    case 0:
+      /* No Grouping */
+      if (ng == 0)
+        switch (scidx) {
+          /* Pilot subcarriers */
+          case -21: case -7: case 7: case 21:
+          /* DC subcarrier */
+          case 0:
+            scidx++;
+          default:
+            break;
+        }
+      break;
+    /* 40 MHz */
+    case 1:
+      /* No Grouping */
+      if (ng == 0)
+        switch (scidx) {
+          /* Pilot subcarriers */
+          case -53: case -25: case -11: case 11: case 25: case 53:
+            scidx++;
+            break;
+          /* DC subcarriers */
+          case -1: case 0: case 1:
+            scidx = 2;
+          default:
+            break;
+        }
+      break;
+    /* 80 MHz */
+    case 2:
+      /* No Grouping */
+      if (ng == 0)
+        switch (scidx) {
+          /* Pilot subcarriers */
+          case -103: case -75: case -39: case -11: case 11: case 39: case 75: case 103:
+            scidx++;
+            break;
+          /* DC subcarriers, skip -1,0, 1 */
+          case -1:
+            scidx = 2;
+          default:
+            break;
+        }
+      break;
+    /* 160 MHz / 80+80 Mhz
+     * Skip values here assume 160 MHz, as vht_mimo_control_t does not let us differentiate
+     * between 160 MHz & 80-80MHz */
+    case 3:
+      switch (ng) {
+        /* No Grouping */
+        case 0:
+          /* DC subcarriers, skip -5 to 5*/
+          if (scidx == -5) {
+            scidx = 6;
+            break;
+          }
+          switch (scidx) {
+            /* Pilot subcarriers */
+            case -231: case -203: case -167: case -139: case -117: case -89: case -53: case -25:
+            case 25: case 53: case 89: case 117: case 139: case 167: case 203: case 231:
+              scidx++;
+              break;
+            /* Other subcarriers, skip -129 to -127, 127 to 129 */
+            case -129:
+              scidx = -126;
+              break;
+            case 127:
+              scidx = 130;
+              break;
+            default:
+              break;
+          }
+          break;
+        /* Grouping of 2 */
+        case 1:
+          switch (scidx) {
+            /* DC subcarriers */
+            case -128: case -4: case -2: case 0: case 2: case 4: case 128:
+              scidx++;
+            default:
+              break;
+          }
+          break;
+        /* Grouping of 4 */
+        case 2:
+          if (scidx == -2 || scidx == 2)
+            scidx++;
+          break;
+      }
+      break;
+    default:
+      break;
+  }
+
+  return scidx;
+}
+
+static guint
+add_ff_vht_compressed_beamforming_report(proto_tree *tree, tvbuff_t *tvb, packet_info *pinfo _U_, int offset, vht_mimo_control_t *vht_cntrl)
+{
+  proto_item *vht_beam_item;
+  proto_tree *vht_beam_tree, *subtree;
+  int i, matrix_size, len, pos, ns, scidx = 0;
+  guint8 phi, psi, carry, ng, nchan_width;
+  /* Table 8-53d Order of angles in the Compressed Beamforming Feedback
+   * Matrix subfield, IEEE Std 802.11ac-2013 amendment */
+  const guint8 na_arr[8][8] = { {  0,  0,  0,  0,  0,  0,  0,  0 },
+                                {  2,  2,  0,  0,  0,  0,  0,  0 },
+                                {  4,  6,  6,  0,  0,  0,  0,  0 },
+                                {  6, 10, 12, 12,  0,  0,  0,  0 },
+                                {  8, 14, 18, 20, 20,  0,  0,  0 },
+                                { 10, 18, 24, 28, 30, 30,  0,  0 },
+                                { 12, 22, 30, 36, 40, 42, 42,  0 },
+                                { 14, 26, 36, 44, 50, 54, 56, 56 }
+                              };
+  /* Table 8-53g Subcarriers for which a Compressed Beamforming Feedback Matrix
+   * subfield is sent back. IEEE Std 802.11ac-2013 amendment */
+  const int ns_arr[4][3] = { {  52,  30,  16 },
+                             { 108,  58,  30 },
+                             { 234, 122,  62 },
+                             { 468, 244, 124 }
+                           };
+
+  vht_beam_item = proto_tree_add_item(tree, hf_ieee80211_vht_compressed_beamforming_report, tvb,
+                                  offset, -1, ENC_NA);
+  vht_beam_tree = proto_item_add_subtree(vht_beam_item, ett_ff_vhtmimo_beamforming_report);
+
+  subtree = proto_tree_add_subtree(vht_beam_tree, tvb, offset, vht_cntrl->nc,
+                        ett_ff_vhtmimo_beamforming_report_snr, NULL, "Average Signal to Noise Ratio");
+
+  for (i = 1; i <= vht_cntrl->nc; i++)
+  {
+    guint8 snr;
+
+    snr = tvb_get_guint8(tvb, offset);
+    proto_tree_add_uint_format(subtree, hf_ieee80211_vht_compressed_beamforming_report_snr, tvb, offset, 1,
+                               snr, "Stream %d - Signal to Noise Ratio: 0x%02X", i, snr);
+    offset += 1;
+  }
+
+  subtree = proto_tree_add_subtree(vht_beam_tree, tvb, offset, -1,
+                        ett_ff_vhtmimo_beamforming_report_feedback_matrices, NULL, "Beamforming Feedback Matrics");
+  if (vht_cntrl->feedback_type) {
+    if (vht_cntrl->codebook_info) {
+      psi = 7; phi = 9;
+    } else {
+      psi = 5; phi = 7;
+    }
+  } else {
+    if (vht_cntrl->codebook_info) {
+      psi = 4; phi = 6;
+    } else {
+      psi = 2; phi = 4;
+    }
+  }
+
+  ng = vht_cntrl->grouping;
+  nchan_width = vht_cntrl->chan_width;
+  ns = ns_arr[nchan_width][ng];
+  switch(nchan_width) {
+    case 0:
+      scidx = -28;
+      break;
+    case 1:
+      scidx = -58;
+      break;
+    case 2:
+      scidx = -122;
+      break;
+    case 3:
+      /* This is -122 for 80+80MHz Channel Width but vht_mimo_control does not allow us
+       * to differentiate between 160MHz and 80+80Mhz */
+      scidx = -250;
+      break;
+  }
+
+  matrix_size = na_arr[vht_cntrl->nr - 1][vht_cntrl->nc -1] * (psi + phi)/2;
+  pos = 0;
+  for (i = 0; i < ns; i++) {
+    if (pos % 8)
+      carry = 1;
+    else
+      carry = 0;
+    len = roundup2((pos + matrix_size), 8)/8 - roundup2(pos, 8)/8;
+    scidx = vht_compressed_skip_scidx(nchan_width, ng, scidx);
+
+    /* TODO : For certain values from na_arr, there is always going be a carry over or overflow from the previous or
+       into the next octet. The largest of possible unaligned values can be 41 bytes long, and masking and shifting
+       whole buffers to show correct values with padding and overflow bits is hence skipped, we only mark the bytes
+       of interest instead */
+    proto_tree_add_none_format(subtree, hf_ieee80211_vht_compressed_beamforming_feedback_matrix, tvb,
+                                    offset - carry, len + carry, "Compressed Beamforming Feedback Matrix for subcarrier %d", scidx++);
+    offset += len;
+    pos += matrix_size;
+  }
+
+  return offset;
+}
+
 static guint
 add_ff_action_vht(proto_tree *tree, tvbuff_t *tvb, packet_info *pinfo, int offset)
 {
   guint start = offset;
   guint8 vht_action;
   proto_item *ti;
+  vht_mimo_control_t vht_mimo_cntrl;
 
   offset += add_fixed_field(tree, tvb, pinfo, offset, FIELD_CATEGORY_CODE);
 
@@ -9116,10 +9360,8 @@ add_ff_action_vht(proto_tree *tree, tvbuff_t *tvb, packet_info *pinfo, int offse
 
   switch(vht_action){
     case VHT_ACT_VHT_COMPRESSED_BEAMFORMING:{
-      offset += add_ff_vht_mimo_cntrl(tree, tvb, pinfo, offset);
-      ti = proto_tree_add_item(tree, hf_ieee80211_vht_compressed_beamforming_report, tvb,
-                          offset, -1, ENC_NA);
-      expert_add_info(pinfo, ti, &ei_ieee80211_vht_action);
+      offset += add_ff_vht_mimo_cntrl(tree, tvb, pinfo, offset, &vht_mimo_cntrl);
+      offset = add_ff_vht_compressed_beamforming_report(tree, tvb, pinfo, offset, &vht_mimo_cntrl);
       offset += tvb_reported_length_remaining(tvb, offset);
     }
     break;
@@ -20333,6 +20575,16 @@ proto_register_ieee80211 (void)
        FT_BYTES, BASE_NONE, NULL, 0,
        NULL, HFILL }},
 
+    {&hf_ieee80211_vht_compressed_beamforming_report_snr,
+      {"Signal to Noise Ratio (SNR)", "wlan.vht.compressed_beamforming_report.snr",
+       FT_UINT8, BASE_HEX, NULL, 0,
+       NULL, HFILL }},
+
+    {&hf_ieee80211_vht_compressed_beamforming_feedback_matrix,
+      {"Compressed Beamforming Feedback Matrix", "wlan.vht.compressed_beamforming_report.feedback_matrix",
+       FT_NONE, BASE_NONE, NULL, 0,
+       NULL, HFILL }},
+
     {&hf_ieee80211_vht_group_id_management,
       {"Group ID Management","wlan.vht.group_id_management",
        FT_BYTES, BASE_NONE, NULL, 0,
@@ -26365,6 +26617,9 @@ proto_register_ieee80211 (void)
     &ett_vht_ndp_annc_sta_info_tree,
 
     &ett_ff_vhtmimo_cntrl,
+    &ett_ff_vhtmimo_beamforming_report,
+    &ett_ff_vhtmimo_beamforming_report_snr,
+    &ett_ff_vhtmimo_beamforming_report_feedback_matrices,
 
     &ett_ht_info_delimiter1_tree,
     &ett_ht_info_delimiter2_tree,