[PATCH 17/18] nvmet-tcp: control messages for recvmsg()

[Hannes Reinecke]

kTLS requires control messages for recvmsg() to relay any out-of-band
TLS messages (eg TLS alerts) to the caller.

Signed-off-by: Hannes Reinecke <hare at suse.de>
---
 drivers/nvme/target/tcp.c | 51 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 49 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/target/tcp.c b/drivers/nvme/target/tcp.c
index ea853658430f..2974abd30b45 100644
--- a/drivers/nvme/target/tcp.c
+++ b/drivers/nvme/target/tcp.c
@@ -13,6 +13,7 @@
 #include <linux/nvme-keyring.h>
 #include <net/sock.h>
 #include <net/tcp.h>
+#include <net/tls.h>
 #include <net/handshake.h>
 #include <linux/inet.h>
 #include <linux/llist.h>
@@ -117,6 +118,7 @@ struct nvmet_tcp_cmd {
 	u32				pdu_len;
 	u32				pdu_recv;
 	int				sg_idx;
+	char				recv_cbuf[CMSG_LEN(sizeof(char))];
 	struct msghdr			recv_msg;
 	struct bio_vec			*iov;
 	u32				flags;
@@ -1103,12 +1105,39 @@ static inline bool nvmet_tcp_pdu_valid(u8 type)
 	return false;
 }
 
+static bool nvmet_tcp_tls_record_ok(struct msghdr *msg, char *cbuf)
+{
+	struct cmsghdr *cmsg = (struct cmsghdr *)cbuf;
+	unsigned char ctype;
+
+	if (!IS_ENABLED(CONFIG_NVME_TARGET_TCP_TLS))
+		return 0;
+
+	if (CMSG_OK(msg, cmsg) &&
+	    cmsg->cmsg_level == SOL_TLS &&
+	    cmsg->cmsg_type == TLS_GET_RECORD_TYPE) {
+		ctype = *((unsigned char *)CMSG_DATA(cmsg));
+		if (ctype != TLS_RECORD_TYPE_DATA) {
+			pr_err("unhandled TLS record %d\n", ctype);
+			return false;
+		}
+	}
+	return true;
+}
+
 static int nvmet_tcp_try_recv_pdu(struct nvmet_tcp_queue *queue)
 {
 	struct nvme_tcp_hdr *hdr = &queue->pdu.cmd.hdr;
 	int len;
 	struct kvec iov;
-	struct msghdr msg = { .msg_flags = MSG_DONTWAIT };
+	char cbuf[CMSG_LEN(sizeof(char))] = {};
+	struct msghdr msg = {
+#ifdef CONFIG_NVME_TARGET_TCP_TLS
+		.msg_control = cbuf,
+		.msg_controllen = sizeof(cbuf),
+#endif
+		.msg_flags = MSG_DONTWAIT
+	};
 
 recv:
 	iov.iov_base = (void *)&queue->pdu + queue->offset;
@@ -1117,6 +1146,8 @@ static int nvmet_tcp_try_recv_pdu(struct nvmet_tcp_queue *queue)
 			iov.iov_len, msg.msg_flags);
 	if (unlikely(len < 0))
 		return len;
+	if (!nvmet_tcp_tls_record_ok(&msg, cbuf))
+		return -ENOTCONN;
 
 	queue->offset += len;
 	queue->left -= len;
@@ -1176,6 +1207,9 @@ static int nvmet_tcp_try_recv_data(struct nvmet_tcp_queue *queue)
 			cmd->recv_msg.msg_flags);
 		if (ret <= 0)
 			return ret;
+		if (!nvmet_tcp_tls_record_ok(&cmd->recv_msg,
+					     cmd->recv_cbuf))
+			return -ENOTCONN;
 
 		cmd->pdu_recv += ret;
 		cmd->rbytes_done += ret;
@@ -1197,7 +1231,14 @@ static int nvmet_tcp_try_recv_ddgst(struct nvmet_tcp_queue *queue)
 {
 	struct nvmet_tcp_cmd *cmd = queue->cmd;
 	int ret;
-	struct msghdr msg = { .msg_flags = MSG_DONTWAIT };
+	char cbuf[CMSG_LEN(sizeof(char))] = {};
+	struct msghdr msg = {
+#ifdef CONFIG_NVME_TARGET_TCP_TLS
+		.msg_control = cbuf,
+		.msg_controllen = sizeof(cbuf),
+#endif
+		.msg_flags = MSG_DONTWAIT
+	};
 	struct kvec iov = {
 		.iov_base = (void *)&cmd->recv_ddgst + queue->offset,
 		.iov_len = queue->left
@@ -1207,6 +1248,8 @@ static int nvmet_tcp_try_recv_ddgst(struct nvmet_tcp_queue *queue)
 			iov.iov_len, msg.msg_flags);
 	if (unlikely(ret < 0))
 		return ret;
+	if (!nvmet_tcp_tls_record_ok(&msg, cbuf))
+		return -ENOTCONN;
 
 	queue->offset += ret;
 	queue->left -= ret;
@@ -1376,6 +1419,10 @@ static int nvmet_tcp_alloc_cmd(struct nvmet_tcp_queue *queue,
 	if (!c->r2t_pdu)
 		goto out_free_data;
 
+	if (IS_ENABLED(CONFIG_NVME_TARGET_TCP_TLS)) {
+		c->recv_msg.msg_control = c->recv_cbuf;
+		c->recv_msg.msg_controllen = sizeof(c->recv_cbuf);
+	}
 	c->recv_msg.msg_flags = MSG_DONTWAIT | MSG_NOSIGNAL;
 
 	list_add_tail(&c->entry, &queue->free_list);
-- 
2.35.3