diff --git a/lib/iscsi/conn.c b/lib/iscsi/conn.c
index 1df42db42..5f28396a6 100644
--- a/lib/iscsi/conn.c
+++ b/lib/iscsi/conn.c
@@ -51,6 +51,12 @@
 #include "iscsi/tgt_node.h"
 #include "iscsi/portal_grp.h"
 
+#define MAKE_DIGEST_WORD(BUF, CRC32C) \
+        (   ((*((uint8_t *)(BUF)+0)) = (uint8_t)((uint32_t)(CRC32C) >> 0)), \
+            ((*((uint8_t *)(BUF)+1)) = (uint8_t)((uint32_t)(CRC32C) >> 8)), \
+            ((*((uint8_t *)(BUF)+2)) = (uint8_t)((uint32_t)(CRC32C) >> 16)), \
+            ((*((uint8_t *)(BUF)+3)) = (uint8_t)((uint32_t)(CRC32C) >> 24)))
+
 #define SPDK_ISCSI_CONNECTION_MEMSET(conn)		\
 	memset(&(conn)->portal, 0, sizeof(*(conn)) -	\
 		offsetof(struct spdk_iscsi_conn, portal));
@@ -1261,6 +1267,22 @@ spdk_iscsi_conn_flush_pdus(void *_conn)
 void
 spdk_iscsi_conn_write_pdu(struct spdk_iscsi_conn *conn, struct spdk_iscsi_pdu *pdu)
 {
+	uint32_t crc32c;
+
+	if (pdu->bhs.opcode != ISCSI_OP_LOGIN_RSP) {
+		/* Header Digest */
+		if (conn->header_digest) {
+			crc32c = spdk_iscsi_pdu_calc_header_digest(pdu);
+			MAKE_DIGEST_WORD(pdu->header_digest, crc32c);
+		}
+
+		/* Data Digest */
+		if (conn->data_digest && DGET24(pdu->bhs.data_segment_len) != 0) {
+			crc32c = spdk_iscsi_pdu_calc_data_digest(pdu);
+			MAKE_DIGEST_WORD(pdu->data_digest, crc32c);
+		}
+	}
+
 	TAILQ_INSERT_TAIL(&conn->write_pdu_list, pdu, tailq);
 	spdk_iscsi_conn_flush_pdus(conn);
 }
diff --git a/lib/iscsi/iscsi.c b/lib/iscsi/iscsi.c
index 007e574a9..4536a3267 100644
--- a/lib/iscsi/iscsi.c
+++ b/lib/iscsi/iscsi.c
@@ -118,12 +118,6 @@ static int spdk_iscsi_reject(struct spdk_iscsi_conn *conn, struct spdk_iscsi_pdu
 	    | (((uint32_t) *((uint8_t *)(BUF)+3)) << 24))	\
 	    == (CRC32C))
 
-#define MAKE_DIGEST_WORD(BUF, CRC32C) \
-	(   ((*((uint8_t *)(BUF)+0)) = (uint8_t)((uint32_t)(CRC32C) >> 0)), \
-	    ((*((uint8_t *)(BUF)+1)) = (uint8_t)((uint32_t)(CRC32C) >> 8)), \
-	    ((*((uint8_t *)(BUF)+2)) = (uint8_t)((uint32_t)(CRC32C) >> 16)), \
-	    ((*((uint8_t *)(BUF)+3)) = (uint8_t)((uint32_t)(CRC32C) >> 24)))
-
 #if 0
 static int
 spdk_match_digest_word(const uint8_t *buf, uint32_t crc32c)
@@ -308,7 +302,7 @@ spdk_islun2lun(uint64_t islun)
 	return lun_i;
 }
 
-static uint32_t
+uint32_t
 spdk_iscsi_pdu_calc_header_digest(struct spdk_iscsi_pdu *pdu)
 {
 	uint32_t crc32c;
@@ -326,7 +320,7 @@ spdk_iscsi_pdu_calc_header_digest(struct spdk_iscsi_pdu *pdu)
 	return crc32c;
 }
 
-static uint32_t
+uint32_t
 spdk_iscsi_pdu_calc_data_digest(struct spdk_iscsi_pdu *pdu)
 {
 	uint32_t data_len = DGET24(pdu->bhs.data_segment_len);
@@ -574,7 +568,6 @@ spdk_iscsi_build_iovecs(struct spdk_iscsi_conn *conn, struct iovec *iovec,
 			struct spdk_iscsi_pdu *pdu)
 {
 	int iovec_cnt = 0;
-	uint32_t crc32c;
 	int enable_digest;
 	int total_ahs_len;
 	int data_len;
@@ -602,9 +595,6 @@ spdk_iscsi_build_iovecs(struct spdk_iscsi_conn *conn, struct iovec *iovec,
 
 	/* Header Digest */
 	if (enable_digest && conn->header_digest) {
-		crc32c = spdk_iscsi_pdu_calc_header_digest(pdu);
-		MAKE_DIGEST_WORD(pdu->header_digest, crc32c);
-
 		iovec[iovec_cnt].iov_base = pdu->header_digest;
 		iovec[iovec_cnt].iov_len = ISCSI_DIGEST_LEN;
 		iovec_cnt++;
@@ -619,9 +609,6 @@ spdk_iscsi_build_iovecs(struct spdk_iscsi_conn *conn, struct iovec *iovec,
 
 	/* Data Digest */
 	if (enable_digest && conn->data_digest && data_len != 0) {
-		crc32c = spdk_iscsi_pdu_calc_data_digest(pdu);
-		MAKE_DIGEST_WORD(pdu->data_digest, crc32c);
-
 		iovec[iovec_cnt].iov_base = pdu->data_digest;
 		iovec[iovec_cnt].iov_len = ISCSI_DIGEST_LEN;
 		iovec_cnt++;
diff --git a/lib/iscsi/iscsi.h b/lib/iscsi/iscsi.h
index 3cfb20fcd..7334f843b 100644
--- a/lib/iscsi/iscsi.h
+++ b/lib/iscsi/iscsi.h
@@ -435,6 +435,8 @@ int spdk_iscsi_copy_param2var(struct spdk_iscsi_conn *conn);
 
 void spdk_iscsi_task_cpl(struct spdk_scsi_task *scsi_task);
 void spdk_iscsi_task_mgmt_cpl(struct spdk_scsi_task *scsi_task);
+uint32_t spdk_iscsi_pdu_calc_header_digest(struct spdk_iscsi_pdu *pdu);
+uint32_t spdk_iscsi_pdu_calc_data_digest(struct spdk_iscsi_pdu *pdu);
 
 /* Memory management */
 void spdk_put_pdu(struct spdk_iscsi_pdu *pdu);
diff --git a/test/unit/lib/iscsi/conn.c/conn_ut.c b/test/unit/lib/iscsi/conn.c/conn_ut.c
index 88d23423b..45296d893 100644
--- a/test/unit/lib/iscsi/conn.c/conn_ut.c
+++ b/test/unit/lib/iscsi/conn.c/conn_ut.c
@@ -279,6 +279,18 @@ spdk_iscsi_tgt_node_cleanup_luns(struct spdk_iscsi_conn *conn,
 	return 0;
 }
 
+uint32_t
+spdk_iscsi_pdu_calc_header_digest(struct spdk_iscsi_pdu *pdu)
+{
+	return 0;
+}
+
+uint32_t
+spdk_iscsi_pdu_calc_data_digest(struct spdk_iscsi_pdu *pdu)
+{
+	return 0;
+}
+
 void
 spdk_shutdown_iscsi_conns_done(void)
 {