diff --git a/sys/dev/nvmf/nvmf_tcp.h b/sys/dev/nvmf/nvmf_tcp.h
new file mode 100644
--- /dev/null
+++ b/sys/dev/nvmf/nvmf_tcp.h
@@ -0,0 +1,276 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2022-2024 Chelsio Communications, Inc.
+ * Written by: John Baldwin <jhb@FreeBSD.org>
+ */
+
+#ifndef __NVMF_TCP_H__
+#define	__NVMF_TCP_H__
+
+#ifndef _KERNEL
+#define	__assert_unreachable	__unreachable
+#define	MPASS			assert
+#endif
+
+#define	NVME_SGL_TYPE_ICD						\
+	NVME_SGL_TYPE(NVME_SGL_TYPE_DATA_BLOCK, NVME_SGL_SUBTYPE_OFFSET)
+
+#define	NVME_SGL_TYPE_COMMAND_BUFFER					\
+	NVME_SGL_TYPE(NVME_SGL_TYPE_TRANSPORT_DATA_BLOCK,		\
+	    NVME_SGL_SUBTYPE_TRANSPORT)
+
+/*
+ * Validate common fields in a received PDU header.  If an error is
+ * detected that requires an immediate disconnect, ECONNRESET is
+ * returned.  If an error is detected that should be reported, EBADMSG
+ * is returned and *fes and *fei are set to the values to be used in a
+ * termination request PDU.  If no error is detected, 0 is returned
+ * and *data_lenp is set to the length of any included data.
+ *
+ * Section number references refer to NVM Express over Fabrics
+ * Revision 1.1 dated October 22, 2019.
+ */
+static __inline int
+nvmf_tcp_validate_pdu_header(const struct nvme_tcp_common_pdu_hdr *ch,
+    bool controller, bool header_digests, bool data_digests, uint8_t rxpda,
+    uint32_t *data_lenp, uint16_t *fes, uint32_t *fei)
+{
+	uint32_t data_len, plen;
+	u_int expected_hlen, full_hlen;
+	uint8_t digest_flags, valid_flags;
+
+	plen = le32toh(ch->plen);
+
+	/*
+	 * Errors must be reported for the lowest incorrect field
+	 * first, so validate fields in order.
+	 */
+
+	/* Validate pdu_type. */
+
+	/* Controllers only receive PDUs with a PDU direction of 0. */
+	if (controller != (ch->pdu_type & 0x01) == 0) {
+		printf("NVMe/TCP: Invalid PDU type %u\n", ch->pdu_type);
+		*fes = NVME_TCP_TERM_REQ_FES_INVALID_HEADER_FIELD;
+		*fei = offsetof(struct nvme_tcp_common_pdu_hdr, pdu_type);
+		return (EBADMSG);
+	}
+
+	switch (ch->pdu_type) {
+	case NVME_TCP_PDU_TYPE_IC_REQ:
+	case NVME_TCP_PDU_TYPE_IC_RESP:
+		/* Shouldn't get these for an established connection. */
+		printf("NVMe/TCP: Received Initialize Connection PDU\n");
+		*fes = NVME_TCP_TERM_REQ_FES_INVALID_HEADER_FIELD;
+		*fei = offsetof(struct nvme_tcp_common_pdu_hdr, pdu_type);
+		return (EBADMSG);
+	case NVME_TCP_PDU_TYPE_H2C_TERM_REQ:
+	case NVME_TCP_PDU_TYPE_C2H_TERM_REQ:
+		/*
+		 * 7.4.7 Termination requests with invalid PDU lengths
+		 * result in an immediate connection termination
+		 * without reporting an error.
+		 */
+		if (plen < sizeof(struct nvme_tcp_term_req_hdr) ||
+		    plen > NVME_TCP_TERM_REQ_PDU_MAX_SIZE) {
+			printf("NVMe/TCP: Received invalid termination request\n");
+			return (ECONNRESET);
+		}
+		break;
+	case NVME_TCP_PDU_TYPE_CAPSULE_CMD:
+	case NVME_TCP_PDU_TYPE_CAPSULE_RESP:
+	case NVME_TCP_PDU_TYPE_H2C_DATA:
+	case NVME_TCP_PDU_TYPE_C2H_DATA:
+	case NVME_TCP_PDU_TYPE_R2T:
+		break;
+	default:
+		printf("NVMe/TCP: Invalid PDU type %u\n", ch->pdu_type);
+		*fes = NVME_TCP_TERM_REQ_FES_INVALID_HEADER_FIELD;
+		*fei = offsetof(struct nvme_tcp_common_pdu_hdr, pdu_type);
+		return (EBADMSG);
+	}
+
+	/* Validate flags. */
+	switch (ch->pdu_type) {
+	default:
+		__assert_unreachable();
+		break;
+	case NVME_TCP_PDU_TYPE_H2C_TERM_REQ:
+	case NVME_TCP_PDU_TYPE_C2H_TERM_REQ:
+		valid_flags = 0;
+		break;
+	case NVME_TCP_PDU_TYPE_CAPSULE_CMD:
+		valid_flags = NVME_TCP_CH_FLAGS_HDGSTF |
+		    NVME_TCP_CH_FLAGS_DDGSTF;
+		break;
+	case NVME_TCP_PDU_TYPE_CAPSULE_RESP:
+	case NVME_TCP_PDU_TYPE_R2T:
+		valid_flags = NVME_TCP_CH_FLAGS_HDGSTF;
+		break;
+	case NVME_TCP_PDU_TYPE_H2C_DATA:
+		valid_flags = NVME_TCP_CH_FLAGS_HDGSTF |
+		    NVME_TCP_CH_FLAGS_DDGSTF | NVME_TCP_H2C_DATA_FLAGS_LAST_PDU;
+		break;
+	case NVME_TCP_PDU_TYPE_C2H_DATA:
+		valid_flags = NVME_TCP_CH_FLAGS_HDGSTF |
+		    NVME_TCP_CH_FLAGS_DDGSTF | NVME_TCP_C2H_DATA_FLAGS_LAST_PDU |
+		    NVME_TCP_C2H_DATA_FLAGS_SUCCESS;
+		break;
+	}
+	if ((ch->flags & ~valid_flags) != 0) {
+		printf("NVMe/TCP: Invalid PDU header flags %#x\n", ch->flags);
+		*fes = NVME_TCP_TERM_REQ_FES_INVALID_HEADER_FIELD;
+		*fei = offsetof(struct nvme_tcp_common_pdu_hdr, flags);
+		return (EBADMSG);
+	}
+
+	/* Verify that digests are present iff enabled. */
+	digest_flags = 0;
+	if (header_digests)
+		digest_flags |= NVME_TCP_CH_FLAGS_HDGSTF;
+	if (data_digests)
+		digest_flags |= NVME_TCP_CH_FLAGS_DDGSTF;
+	if ((digest_flags & valid_flags) !=
+	    (ch->flags & (NVME_TCP_CH_FLAGS_HDGSTF |
+	    NVME_TCP_CH_FLAGS_DDGSTF))) {
+		printf("NVMe/TCP: Invalid PDU header flags %#x\n", ch->flags);
+		*fes = NVME_TCP_TERM_REQ_FES_INVALID_HEADER_FIELD;
+		*fei = offsetof(struct nvme_tcp_common_pdu_hdr, flags);
+		return (EBADMSG);
+	}
+
+	/* 7.4.5.2: SUCCESS in C2H requires LAST_PDU */
+	if (ch->pdu_type == NVME_TCP_PDU_TYPE_C2H_DATA &&
+	    (ch->flags & (NVME_TCP_C2H_DATA_FLAGS_LAST_PDU |
+	    NVME_TCP_C2H_DATA_FLAGS_SUCCESS)) ==
+	    NVME_TCP_C2H_DATA_FLAGS_SUCCESS) {
+		printf("NVMe/TCP: Invalid PDU header flags %#x\n", ch->flags);
+		*fes = NVME_TCP_TERM_REQ_FES_INVALID_HEADER_FIELD;
+		*fei = offsetof(struct nvme_tcp_common_pdu_hdr, flags);
+		return (EBADMSG);
+	}
+
+	/* Validate hlen. */
+	switch (ch->pdu_type) {
+	default:
+		__assert_unreachable();
+		break;
+	case NVME_TCP_PDU_TYPE_H2C_TERM_REQ:
+	case NVME_TCP_PDU_TYPE_C2H_TERM_REQ:
+		expected_hlen = sizeof(struct nvme_tcp_term_req_hdr);
+		break;
+	case NVME_TCP_PDU_TYPE_CAPSULE_CMD:
+		expected_hlen = sizeof(struct nvme_tcp_cmd);
+		break;
+	case NVME_TCP_PDU_TYPE_CAPSULE_RESP:
+		expected_hlen = sizeof(struct nvme_tcp_rsp);
+		break;
+	case NVME_TCP_PDU_TYPE_H2C_DATA:
+		expected_hlen = sizeof(struct nvme_tcp_h2c_data_hdr);
+		break;
+	case NVME_TCP_PDU_TYPE_C2H_DATA:
+		expected_hlen = sizeof(struct nvme_tcp_c2h_data_hdr);
+		break;
+	case NVME_TCP_PDU_TYPE_R2T:
+		expected_hlen = sizeof(struct nvme_tcp_r2t_hdr);
+		break;
+	}
+	if (ch->hlen != expected_hlen) {
+		printf("NVMe/TCP: Invalid PDU header length %u\n", ch->hlen);
+		*fes = NVME_TCP_TERM_REQ_FES_INVALID_HEADER_FIELD;
+		*fei = offsetof(struct nvme_tcp_common_pdu_hdr, hlen);
+		return (EBADMSG);
+	}
+
+	/* Validate pdo. */
+	full_hlen = ch->hlen;
+	if ((ch->flags & NVME_TCP_CH_FLAGS_HDGSTF) != 0)
+		full_hlen += sizeof(uint32_t);
+	switch (ch->pdu_type) {
+	default:
+		__assert_unreachable();
+		break;
+	case NVME_TCP_PDU_TYPE_H2C_TERM_REQ:
+	case NVME_TCP_PDU_TYPE_C2H_TERM_REQ:
+	case NVME_TCP_PDU_TYPE_CAPSULE_RESP:
+	case NVME_TCP_PDU_TYPE_R2T:
+		if (ch->pdo != 0) {
+			printf("NVMe/TCP: Invalid PDU data offset %u\n",
+			    ch->pdo);
+			*fes = NVME_TCP_TERM_REQ_FES_INVALID_HEADER_FIELD;
+			*fei = offsetof(struct nvme_tcp_common_pdu_hdr, pdo);
+			return (EBADMSG);
+		}
+		break;
+	case NVME_TCP_PDU_TYPE_CAPSULE_CMD:
+	case NVME_TCP_PDU_TYPE_H2C_DATA:
+	case NVME_TCP_PDU_TYPE_C2H_DATA:
+		/* Permit PDO of 0 if there is no data. */
+		if (full_hlen == plen && ch->pdo == 0)
+			break;
+
+		if (ch->pdo < full_hlen || ch->pdo > plen ||
+		    ch->pdo % rxpda != 0) {
+			printf("NVMe/TCP: Invalid PDU data offset %u\n",
+			    ch->pdo);
+			*fes = NVME_TCP_TERM_REQ_FES_INVALID_HEADER_FIELD;
+			*fei = offsetof(struct nvme_tcp_common_pdu_hdr, pdo);
+			return (EBADMSG);
+		}
+		break;
+	}
+
+	/* Validate plen. */
+	if (plen < ch->hlen) {
+		printf("NVMe/TCP: Invalid PDU length %u\n", plen);
+		*fes = NVME_TCP_TERM_REQ_FES_INVALID_HEADER_FIELD;
+		*fei = offsetof(struct nvme_tcp_common_pdu_hdr, plen);
+		return (EBADMSG);
+	}
+
+	if (plen == full_hlen)
+		data_len = 0;
+	else
+		data_len = plen - ch->pdo;
+	switch (ch->pdu_type) {
+	default:
+		__assert_unreachable();
+		break;
+	case NVME_TCP_PDU_TYPE_H2C_TERM_REQ:
+	case NVME_TCP_PDU_TYPE_C2H_TERM_REQ:
+		/* Checked above. */
+		MPASS(plen <= NVME_TCP_TERM_REQ_PDU_MAX_SIZE);
+		break;
+	case NVME_TCP_PDU_TYPE_CAPSULE_CMD:
+	case NVME_TCP_PDU_TYPE_H2C_DATA:
+	case NVME_TCP_PDU_TYPE_C2H_DATA:
+		if ((ch->flags & NVME_TCP_CH_FLAGS_DDGSTF) != 0 &&
+		    data_len <= sizeof(uint32_t)) {
+			printf("NVMe/TCP: PDU %u too short for digest\n",
+			    ch->pdu_type);
+			*fes = NVME_TCP_TERM_REQ_FES_INVALID_HEADER_FIELD;
+			*fei = offsetof(struct nvme_tcp_common_pdu_hdr, plen);
+			return (EBADMSG);
+		}
+		break;
+	case NVME_TCP_PDU_TYPE_R2T:
+	case NVME_TCP_PDU_TYPE_CAPSULE_RESP:
+		if (data_len != 0) {
+			printf("NVMe/TCP: PDU %u with data length %u\n",
+			    ch->pdu_type, data_len);
+			*fes = NVME_TCP_TERM_REQ_FES_INVALID_HEADER_FIELD;
+			*fei = offsetof(struct nvme_tcp_common_pdu_hdr, plen);
+			return (EBADMSG);
+		}
+		break;
+	}
+
+	if ((ch->flags & NVME_TCP_CH_FLAGS_DDGSTF) != 0)
+		data_len -= sizeof(uint32_t);
+
+	*data_lenp = data_len;
+	return (0);
+}
+
+#endif /* !__NVMF_TCP_H__ */