From 697652085fecf711af5ca70719af0dae6e30652b Mon Sep 17 00:00:00 2001
From: Mathy Vanhoef <Mathy.Vanhoef@cs.kuleuven.be>
Date: Mon, 6 Aug 2018 15:46:29 -0400
Subject: [PATCH] OCV: Add function to verify a received OCI element

ocv_verify_tx_params() verifies that the receive OCI element includes
field values that are compatible with the local channel configuration.

Signed-off-by: Mathy Vanhoef <Mathy.Vanhoef@cs.kuleuven.be>
---
 src/common/ocv.c | 77 ++++++++++++++++++++++++++++++++++++++++++++++++
 src/common/ocv.h |  3 ++
 2 files changed, 80 insertions(+)

diff --git a/src/common/ocv.c b/src/common/ocv.c
index 17f385506..06badfbfb 100644
--- a/src/common/ocv.c
+++ b/src/common/ocv.c
@@ -93,3 +93,80 @@ int ocv_insert_extended_oci(struct wpa_channel_info *ci, u8 *pos)
 	*pos++ = WLAN_EID_EXT_OCV_OCI;
 	return ocv_insert_oci(ci, &pos);
 }
+
+
+int ocv_verify_tx_params(const u8 *oci_ie, size_t oci_ie_len,
+			 struct wpa_channel_info *ci, int tx_chanwidth,
+			 int tx_seg1_idx)
+{
+	struct oci_info oci;
+
+	if (!oci_ie) {
+		os_snprintf(ocv_errorstr, sizeof(ocv_errorstr),
+			    "OCV failed: did not receive mandatory OCI");
+		return -1;
+	}
+
+	if (oci_ie_len != 3) {
+		os_snprintf(ocv_errorstr, sizeof(ocv_errorstr),
+			    "OCV failed: received OCI of unexpected length (%d)",
+			    (int) oci_ie_len);
+		return -1;
+	}
+
+	os_memset(&oci, 0, sizeof(oci));
+	oci.op_class = oci_ie[0];
+	oci.channel = oci_ie[1];
+	oci.seg1_idx = oci_ie[2];
+	if (ocv_derive_all_parameters(&oci) != 0) {
+		os_snprintf(ocv_errorstr, sizeof(ocv_errorstr),
+			    "OCV failed: unable to interpret received OCI");
+		return -1;
+	}
+
+	/* Primary frequency used to send frames to STA must match the STA's */
+	if ((int) ci->frequency != oci.freq) {
+		os_snprintf(ocv_errorstr, sizeof(ocv_errorstr),
+			    "OCV failed: primary channel mismatch in received OCI (we use %d but receiver is using %d)",
+			    ci->frequency, oci.freq);
+		return -1;
+	}
+
+	/* We shouldn't transmit with a higher bandwidth than the STA supports
+	 */
+	if (tx_chanwidth > oci.chanwidth) {
+		os_snprintf(ocv_errorstr, sizeof(ocv_errorstr),
+			    "OCV failed: channel bandwidth mismatch in received OCI (we use %d but receiver only supports %d)",
+			    tx_chanwidth, oci.chanwidth);
+		return -1;
+	}
+
+	/*
+	 * Secondary channel only needs be checked for 40 MHz in the 2.4 GHz
+	 * band. In the 5 GHz band it's verified through the primary frequency.
+	 * Note that the field ci->sec_channel is only filled in when we use
+	 * 40 MHz.
+	 */
+	if (tx_chanwidth == 40 && ci->frequency < 2500 &&
+	    ci->sec_channel != oci.sec_channel) {
+		os_snprintf(ocv_errorstr, sizeof(ocv_errorstr),
+			    "OCV failed: secondary channel mismatch in received OCI (we use %d but receiver is using %d)",
+			    ci->sec_channel, oci.sec_channel);
+		return -1;
+	}
+
+	/*
+	 * When using a 160 or 80+80 MHz channel to transmit, verify that we use
+	 * the same segments as the receiver by comparing frequency segment 1.
+	 */
+	if ((ci->chanwidth == CHAN_WIDTH_160 ||
+	     ci->chanwidth == CHAN_WIDTH_80P80) &&
+	    tx_seg1_idx != oci.seg1_idx) {
+		os_snprintf(ocv_errorstr, sizeof(ocv_errorstr),
+			    "OCV failed: frequency segment 1 mismatch in received OCI (we use %d but receiver is using %d)",
+			    tx_seg1_idx, oci.seg1_idx);
+		return -1;
+	}
+
+	return 0;
+}
diff --git a/src/common/ocv.h b/src/common/ocv.h
index 3f7743876..6379d9d06 100644
--- a/src/common/ocv.h
+++ b/src/common/ocv.h
@@ -33,5 +33,8 @@ int ocv_derive_all_parameters(struct oci_info *oci);
 int ocv_insert_oci(struct wpa_channel_info *ci, u8 **argpos);
 int ocv_insert_oci_kde(struct wpa_channel_info *ci, u8 **argpos);
 int ocv_insert_extended_oci(struct wpa_channel_info *ci, u8 *pos);
+int ocv_verify_tx_params(const u8 *oci_ie, size_t oci_ie_len,
+			 struct wpa_channel_info *ci, int tx_chanwidth,
+			 int tx_seg1_idx);
 
 #endif /* OCV_H */