From: yoe <yoe>
Date: Tue, 14 Aug 2007 06:14:09 +0000 (+0000)
Subject: r274: Patch by Corey Minyard to set a device read-only at negotiate time
X-Git-Url: http://git.alex.org.uk

r274: Patch by Corey Minyard to set a device read-only at negotiate time
---

diff --git a/cliserv.h b/cliserv.h
index 4ccff22..1d8ecae 100644
--- a/cliserv.h
+++ b/cliserv.h
@@ -124,3 +124,7 @@ u64 ntohll(u64 a) {
 }
 #endif
 #define htonll ntohll
+
+/* Flags used between the client and server */
+#define NBD_FLAG_HAS_FLAGS	(1 << 0)	/* Flags are there */
+#define NBD_FLAG_READ_ONLY	(1 << 1)	/* Device is read-only */
diff --git a/nbd-client.c b/nbd-client.c
index 1adf96a..f4836c5 100644
--- a/nbd-client.c
+++ b/nbd-client.c
@@ -27,6 +27,7 @@
 #include <fcntl.h>
 #include <syslog.h>
 #include <stdlib.h>
+#include <sys/mount.h>
 
 #ifndef __GNUC__
 #error I need GCC to work
@@ -59,7 +60,7 @@ int opennet(char *name, int port) {
 	return sock;
 }
 
-u64 negotiate(int sock, int blocksize) {
+void negotiate(int sock, u64 *rsize64, u32 *flags) {
 	u64 magic, size64;
 	char buf[256] = "\0\0\0\0\0\0\0\0\0";
 
@@ -96,15 +97,20 @@ u64 negotiate(int sock, int blocksize) {
 		printf("size = %lu", (unsigned long)(size64));
 #endif
 
-	if (read(sock, &buf, 128) < 0)
+	if (read(sock, flags, sizeof(*flags)) < 0)
 		err("Failed/4: %m\n");
+	*flags = ntohl(*flags);
+
+	if (read(sock, &buf, 124) < 0)
+		err("Failed/5: %m\n");
 	printf("\n");
 
-	return size64;
+	*rsize64 = size64;
 }
 
-void setsizes(int nbd, u64 size64, int blocksize) {
+void setsizes(int nbd, u64 size64, int blocksize, u32 flags) {
 	unsigned long size;
+	int read_only = (flags & NBD_FLAG_READ_ONLY) ? 1 : 0;
 
 #ifdef NBD_SET_SIZE_BLOCKS
 	if (size64/blocksize > (~0UL >> 1))
@@ -129,6 +135,9 @@ void setsizes(int nbd, u64 size64, int blocksize) {
 #endif
 
 	ioctl(nbd, NBD_CLEAR_SOCK);
+
+	if (ioctl(nbd, BLKROSET, (unsigned long) &read_only) < 0)
+		err("Unable to set read-only attribute for device");
 }
 
 void finish_sock(int sock, int nbd, int swap) {
@@ -152,6 +161,7 @@ int main(int argc, char *argv[]) {
 	int swap=0;
 	int cont=0;
 	u64 size64;
+	u32 flags;
 
 	logging();
 
@@ -227,8 +237,8 @@ int main(int argc, char *argv[]) {
 	}
 	argv=NULL; argc=0; /* don't use it later suddenly */
 
-	size64 = negotiate(sock, blocksize);
-	setsizes(nbd, size64, blocksize);
+	negotiate(sock, &size64, &flags);
+	setsizes(nbd, size64, blocksize, flags);
 	finish_sock(sock, nbd, swap);
 
 	/* Go daemon */
@@ -248,14 +258,20 @@ int main(int argc, char *argv[]) {
 				cont=0;
 			} else {
 				if(cont) {
+					u64 new_size;
+					u32 new_flags;
+
 					fprintf(stderr, " Reconnecting\n");
 					close(sock); close(nbd);
 					sock = opennet(hostname, port);
 					nbd = open(nbddev, O_RDWR);
-					if(size64!=negotiate(sock,blocksize)) {
+					negotiate(sock, &new_size, &new_flags);
+					if (size64 != new_size) {
 						err("Size of the device changed. Bye");
 					}
-					setsizes(nbd, size64, blocksize);
+					setsizes(nbd, size64, blocksize,
+								new_flags);
+
 					finish_sock(sock,nbd,swap);
 				}
 			}
diff --git a/nbd-server.c b/nbd-server.c
index 26c8f59..09a5256 100644
--- a/nbd-server.c
+++ b/nbd-server.c
@@ -1027,10 +1027,11 @@ int expwrite(off_t a, char *buf, size_t len, CLIENT *client) {
  * @param client The client we're negotiating with.
  **/
 void negotiate(CLIENT *client) {
-	char zeros[300];
+	char zeros[128];
 	u64 size_host;
+	u32 flags = NBD_FLAG_HAS_FLAGS;
 
-	memset(zeros, '\0', 290);
+	memset(zeros, '\0', sizeof(zeros));
 	if (write(client->net, INIT_PASSWD, 8) < 0)
 		err("Negotiation failed: %m");
 	cliserv_magic = htonll(cliserv_magic);
@@ -1039,7 +1040,12 @@ void negotiate(CLIENT *client) {
 	size_host = htonll((u64)(client->exportsize));
 	if (write(client->net, &size_host, 8) < 0)
 		err("Negotiation failed: %m");
-	if (write(client->net, zeros, 128) < 0)
+	if (client->server->flags & F_READONLY)
+		flags |= NBD_FLAG_READ_ONLY;
+	flags = htonl(flags);
+	if (write(client->net, &flags, 4) < 0)
+		err("Negotiation failed: %m");
+	if (write(client->net, zeros, 124) < 0)
 		err("Negotiation failed: %m");
 }