[PATCH v9 1/9] wifi: mac80211: Use struct instead of macro for PREQ frame

[Masashi Honma <masashi.honma@gmail.com>]

The existing PREQ_IE_* macros access HWMP PREQ frame fields via hardcoded
byte offsets. When the AE (Address Extension) flag is set, an additional
6 bytes appear mid-frame, and the macros handle this with conditional
arithmetic (e.g., AE_F_SET(x) ? x + N+6 : x + N). This approach
obscures the frame layout and is prone to miscalculation.

Introduce typed packed C structs to represent the PREQ frame layout:
  - ieee80211_mesh_hwmp_preq_top: fixed fields before the optional AE
    address
  - ieee80211_mesh_hwmp_preq_bottom: fields after the optional AE address
  - ieee80211_mesh_hwmp_preq_target: per-target fields

Add ieee80211_mesh_hwmp_preq_get_bottom() to locate the bottom struct
correctly based on whether the AE flag is set.

This preparatory refactoring is needed to fix a 2-byte overread of
target_addr in hwmp_preq_frame_process() when AE is enabled, which is
addressed in a subsequent patch.

Signed-off-by: Masashi Honma <masashi.honma@gmail.com>
---
 include/linux/ieee80211-mesh.h | 42 +++++++++++++++++++++
 net/mac80211/mesh_hwmp.c       | 67 ++++++++++++++++------------------
 2 files changed, 74 insertions(+), 35 deletions(-)

diff --git a/include/linux/ieee80211-mesh.h b/include/linux/ieee80211-mesh.h
index 4b829bcb38b6..bf4a544aed00 100644
--- a/include/linux/ieee80211-mesh.h
+++ b/include/linux/ieee80211-mesh.h
@@ -28,12 +28,40 @@ struct ieee80211s_hdr {
 	u8 eaddr2[ETH_ALEN];
 } __packed __aligned(2);
 
+struct ieee80211_mesh_hwmp_preq_target {
+	u8 flags;
+	u8 addr[ETH_ALEN];
+	__le32 sn;
+} __packed;
+
+struct ieee80211_mesh_hwmp_preq_top {
+	u8 flags;
+	u8 hopcount;
+	u8 ttl;
+	__le32 preq_id;
+	u8 orig_addr[ETH_ALEN];
+	__le32 orig_sn;
+
+	/* optional AE, lifetime, metric, target */
+	u8 variable[];
+} __packed;
+
+struct ieee80211_mesh_hwmp_preq_bottom {
+	__le32 lifetime;
+	__le32 metric;
+	u8 target_count;
+	struct ieee80211_mesh_hwmp_preq_target targets[];
+} __packed;
+
 /* Mesh flags */
 #define MESH_FLAGS_AE_A4 	0x1
 #define MESH_FLAGS_AE_A5_A6	0x2
 #define MESH_FLAGS_AE		0x3
 #define MESH_FLAGS_PS_DEEP	0x4
 
+/* HWMP IE processing macros */
+#define AE_F			(1<<6)
+
 /**
  * enum ieee80211_preq_flags - mesh PREQ element flags
  *
@@ -227,4 +255,18 @@ enum ieee80211_root_mode_identifier {
 	IEEE80211_PROACTIVE_RANN = 4,
 };
 
+static inline bool ieee80211_mesh_preq_prep_ae_enabled(const u8 *ie)
+{
+	return ie[0] & AE_F;
+}
+
+static inline struct ieee80211_mesh_hwmp_preq_bottom *
+ieee80211_mesh_hwmp_preq_get_bottom(const u8 *ie)
+{
+	struct ieee80211_mesh_hwmp_preq_top *top = (void *)ie;
+
+	return (void *)&top->variable[
+		ieee80211_mesh_preq_prep_ae_enabled(ie) ? ETH_ALEN : 0];
+}
+
 #endif /* LINUX_IEEE80211_MESH_H */
diff --git a/net/mac80211/mesh_hwmp.c b/net/mac80211/mesh_hwmp.c
index 9d89ebcce1c1..1a6a22b185d9 100644
--- a/net/mac80211/mesh_hwmp.c
+++ b/net/mac80211/mesh_hwmp.c
@@ -35,24 +35,11 @@ static inline u16 u16_field_get(const u8 *preq_elem, int offset, bool ae)
 }
 
 /* HWMP IE processing macros */
-#define AE_F			(1<<6)
 #define AE_F_SET(x)		(*x & AE_F)
-#define PREQ_IE_FLAGS(x)	(*(x))
-#define PREQ_IE_HOPCOUNT(x)	(*(x + 1))
-#define PREQ_IE_TTL(x)		(*(x + 2))
-#define PREQ_IE_PREQ_ID(x)	u32_field_get(x, 3, 0)
-#define PREQ_IE_ORIG_ADDR(x)	(x + 7)
-#define PREQ_IE_ORIG_SN(x)	u32_field_get(x, 13, 0)
-#define PREQ_IE_LIFETIME(x)	u32_field_get(x, 17, AE_F_SET(x))
-#define PREQ_IE_METRIC(x) 	u32_field_get(x, 21, AE_F_SET(x))
-#define PREQ_IE_TARGET_F(x)	(*(AE_F_SET(x) ? x + 32 : x + 26))
-#define PREQ_IE_TARGET_ADDR(x) 	(AE_F_SET(x) ? x + 33 : x + 27)
-#define PREQ_IE_TARGET_SN(x) 	u32_field_get(x, 33, AE_F_SET(x))
-
-
-#define PREP_IE_FLAGS(x)	PREQ_IE_FLAGS(x)
-#define PREP_IE_HOPCOUNT(x)	PREQ_IE_HOPCOUNT(x)
-#define PREP_IE_TTL(x)		PREQ_IE_TTL(x)
+
+#define PREP_IE_FLAGS(x)	(*(x))
+#define PREP_IE_HOPCOUNT(x)	(*(x + 1))
+#define PREP_IE_TTL(x)		(*(x + 2))
 #define PREP_IE_ORIG_ADDR(x)	(AE_F_SET(x) ? x + 27 : x + 21)
 #define PREP_IE_ORIG_SN(x)	u32_field_get(x, 27, AE_F_SET(x))
 #define PREP_IE_LIFETIME(x)	u32_field_get(x, 13, AE_F_SET(x))
@@ -415,11 +402,16 @@ static u32 hwmp_route_info_get(struct ieee80211_sub_if_data *sdata,
 
 	switch (action) {
 	case MPATH_PREQ:
-		orig_addr = PREQ_IE_ORIG_ADDR(hwmp_ie);
-		orig_sn = PREQ_IE_ORIG_SN(hwmp_ie);
-		orig_lifetime = PREQ_IE_LIFETIME(hwmp_ie);
-		orig_metric = PREQ_IE_METRIC(hwmp_ie);
-		hopcount = PREQ_IE_HOPCOUNT(hwmp_ie) + 1;
+		struct ieee80211_mesh_hwmp_preq_top *preq_elem_top =
+			(void *)hwmp_ie;
+		struct ieee80211_mesh_hwmp_preq_bottom *preq_elem_bottom =
+			ieee80211_mesh_hwmp_preq_get_bottom(hwmp_ie);
+
+		orig_addr = preq_elem_top->orig_addr;
+		orig_sn = le32_to_cpu(preq_elem_top->orig_sn);
+		orig_lifetime = le32_to_cpu(preq_elem_bottom->lifetime);
+		orig_metric = le32_to_cpu(preq_elem_bottom->metric);
+		hopcount = preq_elem_top->hopcount + 1;
 		break;
 	case MPATH_PREP:
 		/* Originator here refers to the MP that was the target in the
@@ -579,6 +571,11 @@ static void hwmp_preq_frame_process(struct ieee80211_sub_if_data *sdata,
 				    const u8 *preq_elem, u32 orig_metric)
 {
 	struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
+	struct ieee80211_mesh_hwmp_preq_top *preq_elem_top = (void *)preq_elem;
+	struct ieee80211_mesh_hwmp_preq_bottom *preq_elem_bottom =
+		ieee80211_mesh_hwmp_preq_get_bottom(preq_elem);
+	struct ieee80211_mesh_hwmp_preq_target *target =
+		preq_elem_bottom->targets;
 	struct mesh_path *mpath = NULL;
 	const u8 *target_addr, *orig_addr;
 	const u8 *da;
@@ -589,13 +586,13 @@ static void hwmp_preq_frame_process(struct ieee80211_sub_if_data *sdata,
 	bool root_is_gate;
 
 	/* Update target SN, if present */
-	target_addr = PREQ_IE_TARGET_ADDR(preq_elem);
-	orig_addr = PREQ_IE_ORIG_ADDR(preq_elem);
-	target_sn = PREQ_IE_TARGET_SN(preq_elem);
-	orig_sn = PREQ_IE_ORIG_SN(preq_elem);
-	target_flags = PREQ_IE_TARGET_F(preq_elem);
+	target_addr = target[0].addr;
+	orig_addr = preq_elem_top->orig_addr;
+	target_sn = le32_to_cpu(target[0].sn);
+	orig_sn = le32_to_cpu(preq_elem_top->orig_sn);
+	target_flags = target[0].flags;
 	/* Proactive PREQ gate announcements */
-	flags = PREQ_IE_FLAGS(preq_elem);
+	flags = preq_elem_top->flags;
 	root_is_gate = !!(flags & RANN_FLAG_IS_GATE);
 
 	mhwmp_dbg(sdata, "received PREQ from %pM\n", orig_addr);
@@ -655,7 +652,7 @@ static void hwmp_preq_frame_process(struct ieee80211_sub_if_data *sdata,
 	}
 
 	if (reply) {
-		lifetime = PREQ_IE_LIFETIME(preq_elem);
+		lifetime = le32_to_cpu(preq_elem_bottom->lifetime);
 		ttl = ifmsh->mshcfg.element_ttl;
 		if (ttl != 0) {
 			mhwmp_dbg(sdata, "replying to the PREQ\n");
@@ -673,22 +670,22 @@ static void hwmp_preq_frame_process(struct ieee80211_sub_if_data *sdata,
 		u32 preq_id;
 		u8 hopcount;
 
-		ttl = PREQ_IE_TTL(preq_elem);
-		lifetime = PREQ_IE_LIFETIME(preq_elem);
+		ttl = preq_elem_top->ttl;
+		lifetime = le32_to_cpu(preq_elem_bottom->lifetime);
 		if (ttl <= 1) {
 			ifmsh->mshstats.dropped_frames_ttl++;
 			return;
 		}
 		mhwmp_dbg(sdata, "forwarding the PREQ from %pM\n", orig_addr);
 		--ttl;
-		preq_id = PREQ_IE_PREQ_ID(preq_elem);
-		hopcount = PREQ_IE_HOPCOUNT(preq_elem) + 1;
+		preq_id = le32_to_cpu(preq_elem_top->preq_id);
+		hopcount = preq_elem_top->hopcount + 1;
 		da = (mpath && mpath->is_root) ?
 			mpath->rann_snd_addr : broadcast_addr;
 
 		if (flags & IEEE80211_PREQ_PROACTIVE_PREP_FLAG) {
-			target_addr = PREQ_IE_TARGET_ADDR(preq_elem);
-			target_sn = PREQ_IE_TARGET_SN(preq_elem);
+			target_addr = target[0].addr;
+			target_sn = le32_to_cpu(target[0].sn);
 		}
 
 		mesh_path_sel_frame_tx(MPATH_PREQ, flags, orig_addr,
-- 
2.43.0