libosdp: Set PD address to 0x7F for broadcast packets

According to the OSDP specification, section "5.9 Packet Format", the PD has to respond to broadcast packets with address 0x7F instead of it's own. This patch addresses this issue. Fixes: #143 Signed-off-by: Siddharth Chandrasekaran <[email protected]>
goToMain · Dec 9, 2023 · 02c41cc · 02c41cc
1 parent 068bf59
commit 02c41cc
Show file tree

Hide file tree

Showing 2 changed files with 14 additions and 0 deletions.
diff --git a/src/osdp_common.h b/src/osdp_common.h
@@ -199,6 +199,7 @@ union osdp_ephemeral_data {
 #define PD_FLAG_PKT_HAS_MARK   BIT(11) /* Packet has mark byte */
 #define PD_FLAG_HAS_SCBK       BIT(12) /* PD has a dedicated SCBK */
 #define PD_FLAG_SC_DISABLED    BIT(13) /* master_key=NULL && scbk=NULL */
+#define PD_FLAG_PKT_BROADCAST  BIT(14) /* this packet was addressed to 0x7F */
 
 enum osdp_cp_phy_state_e {
 	OSDP_CP_PHY_STATE_IDLE,

diff --git a/src/osdp_phy.c b/src/osdp_phy.c
@@ -181,6 +181,10 @@ int osdp_phy_packet_init(struct osdp_pd *pd, uint8_t *buf, int max_len)
 	pkt->pd_address = pd->address & 0x7F;	/* Use only the lower 7 bits */
 	if (is_pd_mode(pd)) {
 		/* PD must reply with MSB of it's address set */
+		if (ISSET_FLAG(pd, PD_FLAG_PKT_BROADCAST)) {
+			pkt->pd_address = 0x7F; /* made 0xFF below */
+			CLEAR_FLAG(pd, PD_FLAG_PKT_BROADCAST);
+		}
 		pkt->pd_address |= 0x80;
 		id = pd->reply_id;
 	} else {
@@ -446,6 +450,15 @@ static int phy_check_packet(struct osdp_pd *pd, uint8_t *buf, int pkt_len)
 			pd->seq_number -= 1;
 			LOG_INF("received a sequence repeat packet!");
 		}
+		/**
+		 * For packets addressed to the broadcast address, the reply
+		 * must have address set to 0x7F and not the current PD's
+		 * address. To handle this case, let's capture this state in PD
+		 * flags.
+		 */
+		if (pd_addr == 0x7F) {
+			SET_FLAG(pd, PD_FLAG_PKT_BROADCAST);
+		}
 	} else {
 		if (comp == 0) {
 			/**