[PATCH RFC 03/15] SUNRPC: Capture cmsg metadata on client-side receive

[Chuck Lever <chuck.lever@xxxxxxxxxx>]

kTLS sockets use cmsg to report decryption errors and the need
for session re-keying. An "application data" message contains a ULP
payload, and that is passed along to the RPC client. An "alert"
message triggers connection reset. Everything else is discarded.

Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
 include/net/tls.h             |    2 ++
 include/trace/events/sunrpc.h |   40 +++++++++++++++++++++++++++++++++
 net/sunrpc/xprtsock.c         |   49 +++++++++++++++++++++++++++++++++++++++--
 3 files changed, 89 insertions(+), 2 deletions(-)

diff --git a/include/net/tls.h b/include/net/tls.h
index 6b1bf46daa34..54bccb2e4014 100644
--- a/include/net/tls.h
+++ b/include/net/tls.h
@@ -71,6 +71,8 @@ static inline struct tlsh_sock *tlsh_sk(struct sock *sk)
 
 #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
diff --git a/include/trace/events/sunrpc.h b/include/trace/events/sunrpc.h
index a66aa1f59ed8..49b748c03610 100644
--- a/include/trace/events/sunrpc.h
+++ b/include/trace/events/sunrpc.h
@@ -1286,6 +1286,46 @@ TRACE_EVENT(xs_data_ready,
 	TP_printk("peer=[%s]:%s", __get_str(addr), __get_str(port))
 );
 
+/*
+ * From https://www.iana.org/assignments/tls-parameters/tls-parameters.xhtml
+ *
+ * Captured March 2022. Other values are unassigned or reserved.
+ */
+#define rpc_show_tls_content_type(type) \
+	__print_symbolic(type, \
+		{ 20,		"change cipher spec" }, \
+		{ 21,		"alert" }, \
+		{ 22,		"handshake" }, \
+		{ 23,		"application data" }, \
+		{ 24,		"heartbeat" }, \
+		{ 25,		"tls12_cid" }, \
+		{ 26,		"ACK" })
+
+TRACE_EVENT(xs_tls_contenttype,
+	TP_PROTO(
+		const struct rpc_xprt *xprt,
+		unsigned char ctype
+	),
+
+	TP_ARGS(xprt, ctype),
+
+	TP_STRUCT__entry(
+		__string(addr, xprt->address_strings[RPC_DISPLAY_ADDR])
+		__string(port, xprt->address_strings[RPC_DISPLAY_PORT])
+		__field(unsigned long, ctype)
+	),
+
+	TP_fast_assign(
+		__assign_str(addr, xprt->address_strings[RPC_DISPLAY_ADDR]);
+		__assign_str(port, xprt->address_strings[RPC_DISPLAY_PORT]);
+		__entry->ctype = ctype;
+	),
+
+	TP_printk("peer=[%s]:%s: %s", __get_str(addr), __get_str(port),
+		rpc_show_tls_content_type(__entry->ctype)
+	)
+);
+
 TRACE_EVENT(xs_stream_read_data,
 	TP_PROTO(struct rpc_xprt *xprt, ssize_t err, size_t total),
 
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index b5bc03c52b9b..e42ae84d7359 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -47,6 +47,8 @@
 #include <net/checksum.h>
 #include <net/udp.h>
 #include <net/tcp.h>
+#include <net/tls.h>
+
 #include <linux/bvec.h>
 #include <linux/highmem.h>
 #include <linux/uio.h>
@@ -350,13 +352,56 @@ xs_alloc_sparse_pages(struct xdr_buf *buf, size_t want, gfp_t gfp)
 	return want;
 }
 
+static int
+xs_sock_process_cmsg(struct socket *sock, 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));
+
+		trace_xs_tls_contenttype(xprt_from_sock(sock->sk), content_type);
+		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
+xs_sock_recv_cmsg(struct socket *sock, struct msghdr *msg, int flags)
+{
+	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(sock, msg, flags);
+	if (msg->msg_controllen != sizeof(u))
+		ret = xs_sock_process_cmsg(sock, msg, &u.cmsg, ret);
+	return ret;
+}
+
 static ssize_t
 xs_sock_recvmsg(struct socket *sock, struct msghdr *msg, int flags, size_t seek)
 {
 	ssize_t ret;
 	if (seek != 0)
 		iov_iter_advance(&msg->msg_iter, seek);
-	ret = sock_recvmsg(sock, msg, flags);
+	ret = xs_sock_recv_cmsg(sock, msg, flags);
 	return ret > 0 ? ret + seek : ret;
 }
 
@@ -382,7 +427,7 @@ xs_read_discard(struct socket *sock, struct msghdr *msg, int flags,
 		size_t count)
 {
 	iov_iter_discard(&msg->msg_iter, READ, count);
-	return sock_recvmsg(sock, msg, flags);
+	return xs_sock_recv_cmsg(sock, msg, flags);
 }
 
 #if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE