[lxc-devel] [PATCH 1/2] command socket: use hash if needed

[Serge Hallyn]

The container command socket is an abstract unix socket containing
the lxcpath and container name.  Those can be too long.  In that case,
use the hash of the lxcpath and lxcname.  Continue to use the path and
name if possible to avoid any back compat issues.

Signed-off-by: Serge Hallyn <serge.hallyn at ubuntu.com>
---
 src/lxc/commands.c | 32 +++++++++++++++++++++++++++-----
 1 file changed, 27 insertions(+), 5 deletions(-)

diff --git a/src/lxc/commands.c b/src/lxc/commands.c
index 458d41e..f46efc5 100644
--- a/src/lxc/commands.c
+++ b/src/lxc/commands.c
@@ -28,6 +28,7 @@
 #include <fcntl.h>
 #include <poll.h>
 #include <sys/socket.h>
+#include <inttypes.h>
 #include <sys/un.h>
 #include <sys/param.h>
 #include <malloc.h>
@@ -74,24 +75,45 @@
 lxc_log_define(lxc_commands, lxc);
 
 static int fill_sock_name(char *path, int len, const char *name,
-			  const char *inpath)
+			  const char *lxcpath)
 {
-	const char *lxcpath = NULL;
+	char *tmppath;
+	size_t tmplen;
+	uint64_t hash;
 	int ret;
 
-	if (!inpath) {
+	if (!lxcpath) {
 		lxcpath = lxc_global_config_value("lxc.lxcpath");
 		if (!lxcpath) {
 			ERROR("Out of memory getting lxcpath");
 			return -1;
 		}
 	}
-	ret = snprintf(path, len, "%s/%s/command", lxcpath ? lxcpath : inpath, name);
+		
+	ret = snprintf(path, len, "%s/%s/command", lxcpath, name);
 
+	if (ret < 0) {
+		ERROR("Error writing to command sock path");
+		return -1;
+	}
+	if (ret < len)
+		return 0;
+
+	/* ret >= len; lxcpath or name is too long.  hash both */
+	tmplen = strlen(name) + strlen(lxcpath) + 2;
+	tmppath = alloca(tmplen);
+	ret = snprintf(tmppath, tmplen, "%s/%s", lxcpath, name);
+	if (ret < 0 || ret >= tmplen) {
+		ERROR("memory error");
+		return -1;
+	}
+	hash = fnv_64a_buf(tmppath, ret, FNV1A_64_INIT);
+	ret = snprintf(path, len, "lxc/%016" PRIx64 "/cmd_sock", hash);
 	if (ret < 0 || ret >= len) {
-		ERROR("Name too long");
+		ERROR("Command socket name too long");
 		return -1;
 	}
+
 	return 0;
 }
 
-- 
2.1.0.rc1