ceph: use kernel DNS resolver

Change ceph_parse_ips to take either names given as
IP addresses or standard hostnames (e.g. localhost).
The DNS lookup is done using the dns_resolver facility
similar to its use in AFS, NFS, and CIFS.

This patch defines CONFIG_CEPH_LIB_USE_DNS_RESOLVER
that controls if this feature is on or off.

Signed-off-by: Noah Watkins <noahwatkins@gmail.com>
Signed-off-by: Sage Weil <sage@newdream.net>

diff --git a/net/ceph/Kconfig b/net/ceph/Kconfig
index be683f2d401f9cb95a00b2652a5b87a657d3db2f..cc04dd667a10b9b032c0d10bd3caeb0751ae70c7 100644 (file)
--- a/net/ceph/Kconfig
+++ b/net/ceph/Kconfig
@@ -27,3 +27,17 @@ config CEPH_LIB_PRETTYDEBUG
 
          If unsure, say N.
 
+config CEPH_LIB_USE_DNS_RESOLVER
+       bool "Use in-kernel support for DNS lookup"
+       depends on CEPH_LIB
+       select DNS_RESOLVER
+       default n
+       help
+         If you say Y here, hostnames (e.g. monitor addresses) will
+         be resolved using the CONFIG_DNS_RESOLVER facility.
+
+         For information on how to use CONFIG_DNS_RESOLVER consult
+         Documentation/networking/dns_resolver.txt
+
+         If unsure, say N.
+

diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index f56aca30261776cd630501b79d40f78675d649ec..f466930e26faf9a9b8f43730641cdf5a1b7f7dee 100644 (file)
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -11,6 +11,7 @@
 #include <linux/string.h>
 #include <linux/bio.h>
 #include <linux/blkdev.h>
+#include <linux/dns_resolver.h>
 #include <net/tcp.h>
 
 #include <linux/ceph/libceph.h>
@@ -1077,6 +1078,101 @@ static void addr_set_port(struct sockaddr_storage *ss, int p)
        }
 }
 
+/*
+ * Unlike other *_pton function semantics, zero indicates success.
+ */
+static int ceph_pton(const char *str, size_t len, struct sockaddr_storage *ss,
+               char delim, const char **ipend)
+{
+       struct sockaddr_in *in4 = (void *)ss;
+       struct sockaddr_in6 *in6 = (void *)ss;
+
+       memset(ss, 0, sizeof(*ss));
+
+       if (in4_pton(str, len, (u8 *)&in4->sin_addr.s_addr, delim, ipend)) {
+               ss->ss_family = AF_INET;
+               return 0;
+       }
+
+       if (in6_pton(str, len, (u8 *)&in6->sin6_addr.s6_addr, delim, ipend)) {
+               ss->ss_family = AF_INET6;
+               return 0;
+       }
+
+       return -EINVAL;
+}
+
+/*
+ * Extract hostname string and resolve using kernel DNS facility.
+ */
+#ifdef CONFIG_CEPH_LIB_USE_DNS_RESOLVER
+static int ceph_dns_resolve_name(const char *name, size_t namelen,
+               struct sockaddr_storage *ss, char delim, const char **ipend)
+{
+       const char *end, *delim_p;
+       char *colon_p, *ip_addr = NULL;
+       int ip_len, ret;
+
+       /*
+        * The end of the hostname occurs immediately preceding the delimiter or
+        * the port marker (':') where the delimiter takes precedence.
+        */
+       delim_p = memchr(name, delim, namelen);
+       colon_p = memchr(name, ':', namelen);
+
+       if (delim_p && colon_p)
+               end = delim_p < colon_p ? delim_p : colon_p;
+       else if (!delim_p && colon_p)
+               end = colon_p;
+       else {
+               end = delim_p;
+               if (!end) /* case: hostname:/ */
+                       end = name + namelen;
+       }
+
+       if (end <= name)
+               return -EINVAL;
+
+       /* do dns_resolve upcall */
+       ip_len = dns_query(NULL, name, end - name, NULL, &ip_addr, NULL);
+       if (ip_len > 0)
+               ret = ceph_pton(ip_addr, ip_len, ss, -1, NULL);
+       else
+               ret = -ESRCH;
+
+       kfree(ip_addr);
+
+       *ipend = end;
+
+       pr_info("resolve '%.*s' (ret=%d): %s\n", (int)(end - name), name,
+                       ret, ret ? "failed" : ceph_pr_addr(ss));
+
+       return ret;
+}
+#else
+static inline int ceph_dns_resolve_name(const char *name, size_t namelen,
+               struct sockaddr_storage *ss, char delim, const char **ipend)
+{
+       return -EINVAL;
+}
+#endif
+
+/*
+ * Parse a server name (IP or hostname). If a valid IP address is not found
+ * then try to extract a hostname to resolve using userspace DNS upcall.
+ */
+static int ceph_parse_server_name(const char *name, size_t namelen,
+                       struct sockaddr_storage *ss, char delim, const char **ipend)
+{
+       int ret;
+
+       ret = ceph_pton(name, namelen, ss, delim, ipend);
+       if (ret)
+               ret = ceph_dns_resolve_name(name, namelen, ss, delim, ipend);
+
+       return ret;
+}
+
 /*
  * Parse an ip[:port] list into an addr array.  Use the default
  * monitor port if a port isn't specified.
@@ -1085,15 +1181,13 @@ int ceph_parse_ips(const char *c, const char *end,
                   struct ceph_entity_addr *addr,
                   int max_count, int *count)
 {
-       int i;
+       int i, ret = -EINVAL;
        const char *p = c;
 
        dout("parse_ips on '%.*s'\n", (int)(end-c), c);
        for (i = 0; i < max_count; i++) {
                const char *ipend;
                struct sockaddr_storage *ss = &addr[i].in_addr;
-               struct sockaddr_in *in4 = (void *)ss;
-               struct sockaddr_in6 *in6 = (void *)ss;
                int port;
                char delim = ',';
 
@@ -1102,15 +1196,11 @@ int ceph_parse_ips(const char *c, const char *end,
                        p++;
                }
 
-               memset(ss, 0, sizeof(*ss));
-               if (in4_pton(p, end - p, (u8 *)&in4->sin_addr.s_addr,
-                            delim, &ipend))
-                       ss->ss_family = AF_INET;
-               else if (in6_pton(p, end - p, (u8 *)&in6->sin6_addr.s6_addr,
-                                 delim, &ipend))
-                       ss->ss_family = AF_INET6;
-               else
+               ret = ceph_parse_server_name(p, end - p, ss, delim, &ipend);
+               if (ret)
                        goto bad;
+               ret = -EINVAL;
+
                p = ipend;
 
                if (delim == ']') {
@@ -1155,7 +1245,7 @@ int ceph_parse_ips(const char *c, const char *end,
 
 bad:
        pr_err("parse_ips bad ip '%.*s'\n", (int)(end - c), c);
-       return -EINVAL;
+       return ret;
 }
 EXPORT_SYMBOL(ceph_parse_ips);