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 (file)
--- 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 (file)
--- 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 (file)
--- 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");
 }