SUNRPC: Recognize control messages in server-side TCP socket code

To support kTLS, the server-side TCP socket receive path needs to
watch for CMSGs.
Acked-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

include/net/tls.h

@@ -69,6 +69,8 @@ extern const struct tls_cipher_size_desc tls_cipher_size_desc[];
 
 #define TLS_CRYPTO_INFO_READY(info)	((info)->cipher_type)
 
+#define TLS_RECORD_TYPE_ALERT		0x15
+#define TLS_RECORD_TYPE_HANDSHAKE	0x16
 #define TLS_RECORD_TYPE_DATA		0x17
 
 #define TLS_AAD_SPACE_SIZE		13

net/sunrpc/svcsock.c

@@ -43,6 +43,7 @@
 #include <net/udp.h>
 #include <net/tcp.h>
 #include <net/tcp_states.h>
+#include <net/tls.h>
 #include <linux/uaccess.h>
 #include <linux/highmem.h>
 #include <asm/ioctls.h>
@@ -216,6 +217,49 @@ static int svc_one_sock_name(struct svc_sock *svsk, char *buf, int remaining)
 	return len;
 }
 
+static int
+svc_tcp_sock_process_cmsg(struct svc_sock *svsk, struct msghdr *msg,
+			  struct cmsghdr *cmsg, int ret)
+{
+	if (cmsg->cmsg_level == SOL_TLS &&
+	    cmsg->cmsg_type == TLS_GET_RECORD_TYPE) {
+		u8 content_type = *((u8 *)CMSG_DATA(cmsg));
+
+		switch (content_type) {
+		case TLS_RECORD_TYPE_DATA:
+			/* TLS sets EOR at the end of each application data
+			 * record, even though there might be more frames
+			 * waiting to be decrypted.
+			 */
+			msg->msg_flags &= ~MSG_EOR;
+			break;
+		case TLS_RECORD_TYPE_ALERT:
+			ret = -ENOTCONN;
+			break;
+		default:
+			ret = -EAGAIN;
+		}
+	}
+	return ret;
+}
+
+static int
+svc_tcp_sock_recv_cmsg(struct svc_sock *svsk, struct msghdr *msg)
+{
+	union {
+		struct cmsghdr	cmsg;
+		u8		buf[CMSG_SPACE(sizeof(u8))];
+	} u;
+	int ret;
+
+	msg->msg_control = &u;
+	msg->msg_controllen = sizeof(u);
+	ret = sock_recvmsg(svsk->sk_sock, msg, MSG_DONTWAIT);
+	if (unlikely(msg->msg_controllen != sizeof(u)))
+		ret = svc_tcp_sock_process_cmsg(svsk, msg, &u.cmsg, ret);
+	return ret;
+}
+
 #if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
 static void svc_flush_bvec(const struct bio_vec *bvec, size_t size, size_t seek)
 {
@@ -263,7 +307,7 @@ static ssize_t svc_tcp_read_msg(struct svc_rqst *rqstp, size_t buflen,
 		iov_iter_advance(&msg.msg_iter, seek);
 		buflen -= seek;
 	}
-	len = sock_recvmsg(svsk->sk_sock, &msg, MSG_DONTWAIT);
+	len = svc_tcp_sock_recv_cmsg(svsk, &msg);
 	if (len > 0)
 		svc_flush_bvec(bvec, len, seek);
 
@@ -877,7 +921,7 @@ static ssize_t svc_tcp_read_marker(struct svc_sock *svsk,
 		iov.iov_base = ((char *)&svsk->sk_marker) + svsk->sk_tcplen;
 		iov.iov_len  = want;
 		iov_iter_kvec(&msg.msg_iter, ITER_DEST, &iov, 1, want);
-		len = sock_recvmsg(svsk->sk_sock, &msg, MSG_DONTWAIT);
+		len = svc_tcp_sock_recv_cmsg(svsk, &msg);
 		if (len < 0)
 			return len;
 		svsk->sk_tcplen += len;