[PATCH v2 08/29] tools/xenlogd: add 9pfs walk request support

[Juergen Gross <jgross@xxxxxxxx>]

Add the walk request of the 9pfs protocol.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
V2:
- don't allow walking across symbolic links
---
 tools/xen-9pfsd/io.c        | 172 ++++++++++++++++++++++++++++++++++++
 tools/xen-9pfsd/xen-9pfsd.h |   1 +
 2 files changed, 173 insertions(+)

diff --git a/tools/xen-9pfsd/io.c b/tools/xen-9pfsd/io.c
index 03e45d5f8b..62c64474e6 100644
--- a/tools/xen-9pfsd/io.c
+++ b/tools/xen-9pfsd/io.c
@@ -27,9 +27,11 @@
 #define P9_CMD_VERSION    100
 #define P9_CMD_ATTACH     104
 #define P9_CMD_ERROR      107
+#define P9_CMD_WALK       110
 
 #define P9_MIN_MSIZE      2048
 #define P9_VERSION        "9P2000.u"
+#define P9_WALK_MAXELEM   16
 
 struct p9_qid {
     uint8_t type;
@@ -459,6 +461,21 @@ static struct p9_fid *find_fid(device *device, unsigned 
int fid)
     return NULL;
 }
 
+static struct p9_fid *get_fid_ref(device *device, unsigned int fid)
+{
+    struct p9_fid *fidp;
+
+    pthread_mutex_lock(&device->fid_mutex);
+
+    fidp = find_fid(device, fid);
+    if ( fidp )
+        fidp->ref++;
+
+    pthread_mutex_unlock(&device->fid_mutex);
+
+    return fidp;
+}
+
 static struct p9_fid *alloc_fid_mem(device *device, unsigned int fid,
                                     const char *path)
 {
@@ -551,6 +568,10 @@ static int fill_qid(const char *path, struct p9_qid *qid,
         stbuf = &st;
     }
 
+    /* Don't allow symbolic links. */
+    if ( S_ISLNK(stbuf->st_mode) )
+        return EMLINK;
+
     qid->type = S_ISDIR(stbuf->st_mode) ? QID_TYPE_DIR : 0;
     qid->version = stbuf->st_mtime ^ (stbuf->st_size << 8);
     qid->path = stbuf->st_ino;
@@ -558,6 +579,20 @@ static int fill_qid(const char *path, struct p9_qid *qid,
     return 0;
 }
 
+static bool name_ok(const char *str)
+{
+    if ( !*str )
+        return false;
+
+    if ( strchr(str, '/' ) )
+        return false;
+
+    if ( !strcmp(str, "..") || !strcmp(str, ".") )
+        return false;
+
+    return true;
+}
+
 static void p9_error(struct ring *ring, uint16_t tag, uint32_t err)
 {
     unsigned int erroff;
@@ -635,6 +670,139 @@ static void p9_attach(struct ring *ring, struct p9_header 
*hdr)
     fill_buffer(ring, hdr->cmd + 1, hdr->tag, "Q", &qid);
 }
 
+static void p9_walk(struct ring *ring, struct p9_header *hdr)
+{
+    device *device = ring->device;
+    uint32_t fid;
+    uint32_t newfid;
+    struct p9_fid *fidp = NULL;
+    struct p9_qid *qids = NULL;
+    unsigned int n_names = 0;
+    unsigned int *names = NULL;
+    unsigned int walked = 0;
+    unsigned int i;
+    char *path = NULL;
+    unsigned int path_len;
+    int ret;
+
+    ret = fill_data(ring, "UUaS", &fid, &newfid, &n_names, &names);
+    if ( n_names > P9_WALK_MAXELEM )
+    {
+        p9_error(ring, hdr->tag, EINVAL);
+        goto out;
+    }
+    if ( ret != 3 + n_names )
+    {
+        p9_error(ring, hdr->tag, errno);
+        goto out;
+    }
+
+    fidp = get_fid_ref(device, fid);
+    if ( !fidp )
+    {
+        p9_error(ring, hdr->tag, ENOENT);
+        goto out;
+    }
+    if ( fidp->opened )
+    {
+        p9_error(ring, hdr->tag, EINVAL);
+        goto out;
+    }
+
+    path_len = strlen(fidp->path) + 1;
+    for ( i = 0; i < n_names; i++ )
+    {
+        if ( !name_ok(ring->str + names[i]) )
+        {
+            p9_error(ring, hdr->tag, ENOENT);
+            goto out;
+        }
+        path_len += strlen(ring->str + names[i]) + 1;
+    }
+    path = calloc(path_len + 1, 1);
+    if ( !path )
+    {
+        p9_error(ring, hdr->tag, ENOMEM);
+        goto out;
+    }
+    strcpy(path, fidp->path);
+
+    if ( n_names )
+    {
+        qids = calloc(n_names, sizeof(*qids));
+        if ( !qids )
+        {
+            p9_error(ring, hdr->tag, ENOMEM);
+            goto out;
+        }
+        for ( i = 0; i < n_names; i++ )
+        {
+            strcat(path, "/");
+            strcat(path, ring->str + names[i]);
+            ret = fill_qid(path, qids + i, NULL);
+            if ( ret )
+            {
+                if ( !walked )
+                {
+                    p9_error(ring, hdr->tag, errno);
+                    goto out;
+                }
+                break;
+            }
+            walked++;
+        }
+    }
+
+    if ( walked == n_names )
+    {
+        const char *rel_path = path + strlen(device->host_path);
+        bool ok = false;
+
+        if ( fid == newfid )
+        {
+            struct p9_fid *new_fidp;
+
+            pthread_mutex_lock(&device->fid_mutex);
+
+            if ( fidp->ref != 2 )
+            {
+                errno = EBUSY;
+            }
+            else
+            {
+                new_fidp = alloc_fid_mem(device, fid, rel_path);
+                if ( new_fidp )
+                {
+                    new_fidp->ref = 2;
+                    XEN_TAILQ_REMOVE(&device->fids, fidp, list);
+                    XEN_TAILQ_INSERT_HEAD(&device->fids, new_fidp, list);
+                    free(fidp);
+                    fidp = new_fidp;
+                    ok = true;
+                }
+            }
+
+            pthread_mutex_unlock(&device->fid_mutex);
+        }
+        else
+            ok = alloc_fid(device, newfid, rel_path);
+
+        if ( !ok )
+        {
+            p9_error(ring, hdr->tag, errno);
+            goto out;
+        }
+    }
+
+    fill_buffer(ring, hdr->cmd + 1, hdr->tag, "aQ", &walked, qids);
+
+ out:
+    free_fid(device, fidp);
+    free(qids);
+    free(path);
+    free(names);
+}
+
 void *io_thread(void *arg)
 {
     struct ring *ring = arg;
@@ -698,6 +866,10 @@ void *io_thread(void *arg)
                 p9_attach(ring, &hdr);
                 break;
 
+            case P9_CMD_WALK:
+                p9_walk(ring, &hdr);
+                break;
+
             default:
                 syslog(LOG_DEBUG, "%u.%u sent unhandled command %u\n",
                        ring->device->domid, ring->device->devid, hdr.cmd);
diff --git a/tools/xen-9pfsd/xen-9pfsd.h b/tools/xen-9pfsd/xen-9pfsd.h
index e511acdb76..75eaac9f7b 100644
--- a/tools/xen-9pfsd/xen-9pfsd.h
+++ b/tools/xen-9pfsd/xen-9pfsd.h
@@ -25,6 +25,7 @@ struct p9_fid {
     XEN_TAILQ_ENTRY(struct p9_fid) list;
     unsigned int fid;
     unsigned int ref;
+    bool opened;
     char path[];
 };
 
-- 
2.35.3