From cb879d9f3744190f47cf44cf9bcb1ef705f056a5 Mon Sep 17 00:00:00 2001
From: Zach Brown <zab@versity.com>
Date: Wed, 11 Oct 2017 11:27:23 -0700
Subject: [PATCH] scoutfs: add network greeting message

Add a network greeting message that's exchanged between the client and
server on every connection to make sure that we have the correct file
system and format hash.

Signed-off-by: Zach Brown <zab@versity.com>
---
 kmod/src/client.c | 30 ++++++++++++++++++++++++++++++
 kmod/src/format.h |  5 +++++
 kmod/src/server.c | 39 ++++++++++++++++++++++++++++++++++++++-
 3 files changed, 73 insertions(+), 1 deletion(-)

diff --git a/kmod/src/client.c b/kmod/src/client.c
index 8cf43653..16517ccb 100644
--- a/kmod/src/client.c
+++ b/kmod/src/client.c
@@ -251,9 +251,11 @@ static int client_connect(struct client_info *client)
 {
 	struct super_block *sb = client->sb;
 	struct scoutfs_super_block super;
+	struct scoutfs_net_greeting greet;
 	struct sockaddr_in *sin;
 	struct socket *sock = NULL;
 	struct timeval tv;
+	struct kvec kv;
 	int retries;
 	int addrlen;
 	int optval;
@@ -323,6 +325,34 @@ static int client_connect(struct client_info *client)
 		if (ret)
 			continue;
 
+		greet.fsid = super.id;
+		greet.format_hash = super.format_hash;
+		kv.iov_base = &greet;
+		kv.iov_len = sizeof(greet);
+		ret = scoutfs_sock_sendmsg(sock, &kv, 1);
+		if (ret)
+			continue;
+
+		ret = scoutfs_sock_recvmsg(sock, &greet, sizeof(greet));
+		if (ret)
+			continue;
+
+		if (greet.fsid != super.id) {
+			scoutfs_warn(sb, "server "SIN_FMT" has fsid 0x%llx, expected 0x%llx",
+				     SIN_ARG(&client->peername),
+				     le64_to_cpu(greet.fsid),
+				     le64_to_cpu(super.id));
+			continue;
+		}
+
+		if (greet.format_hash != super.format_hash) {
+			scoutfs_warn(sb, "server "SIN_FMT" has format hash 0x%llx, expected 0x%llx",
+				     SIN_ARG(&client->peername),
+				     le64_to_cpu(greet.format_hash),
+				     le64_to_cpu(super.format_hash));
+			continue;
+		}
+
 		/* but use a keepalive timeout instead of send timeout */
 		tv.tv_sec = 0;
 		tv.tv_usec = 0;
diff --git a/kmod/src/format.h b/kmod/src/format.h
index d9be949b..ffe5ce44 100644
--- a/kmod/src/format.h
+++ b/kmod/src/format.h
@@ -566,6 +566,11 @@ struct scoutfs_lock_name {
  * messages over the wire.
  */
 
+struct scoutfs_net_greeting {
+	__le64 fsid;
+	__le64 format_hash;
+} __packed;
+
 /*
  * This header precedes and describes all network messages sent over
  * sockets.  The id is set by the request and sent in the reply.  The
diff --git a/kmod/src/server.c b/kmod/src/server.c
index a12da887..007ca7d6 100644
--- a/kmod/src/server.c
+++ b/kmod/src/server.c
@@ -765,11 +765,16 @@ static void scoutfs_server_recv_func(struct work_struct *work)
 						      recv_work);
 	struct server_info *server = conn->server;
 	struct super_block *sb = server->sb;
+	struct scoutfs_sb_info *sbi = SCOUTFS_SB(sb);
+	struct scoutfs_super_block *super = &sbi->super;
 	struct socket *sock = conn->sock;
 	struct workqueue_struct *req_wq;
+	struct scoutfs_net_greeting greet;
 	struct scoutfs_net_header nh;
 	struct server_request *req;
+	bool passed_greeting;
 	unsigned data_len;
+	struct kvec kv;
 	int ret;
 
 	req_wq = alloc_workqueue("scoutfs_server_requests",
@@ -779,13 +784,45 @@ static void scoutfs_server_recv_func(struct work_struct *work)
 		goto out;
 	}
 
-	for (;;) {
+	/* first bounce the greeting */
+	ret = scoutfs_sock_recvmsg(sock, &greet, sizeof(greet));
+	if (ret)
+		goto out;
 
+	/* we'll close conn after failed greeting to let client see ours */
+	passed_greeting = false;
+
+	if (greet.fsid != super->id) {
+		scoutfs_warn(sb, "client "SIN_FMT" has fsid 0x%llx, expected 0x%llx",
+			     SIN_ARG(&conn->peername),
+			     le64_to_cpu(greet.fsid),
+			     le64_to_cpu(super->id));
+	} else if (greet.format_hash != super->format_hash) {
+		scoutfs_warn(sb, "client "SIN_FMT" has format hash 0x%llx, expected 0x%llx",
+			     SIN_ARG(&conn->peername),
+			     le64_to_cpu(greet.format_hash),
+			     le64_to_cpu(super->format_hash));
+	} else {
+		passed_greeting = true;
+	}
+
+	greet.fsid = super->id;
+	greet.format_hash = super->format_hash;
+	kv.iov_base = &greet;
+	kv.iov_len = sizeof(greet);
+	ret = scoutfs_sock_sendmsg(sock, &kv, 1);
+	if (ret)
+		goto out;
+
+	for (;;) {
 		/* receive the header */
 		ret = scoutfs_sock_recvmsg(sock, &nh, sizeof(nh));
 		if (ret)
 			break;
 
+		if (!passed_greeting)
+			break;
+
 		trace_scoutfs_server_recv_request(conn->server->sb,
 						  &conn->sockname,
 						  &conn->peername, &nh);