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Date: Thu, 22 Sep 2011 14:29:14 -0700 (PDT)
From: Sage Weil <sage@...dream.net>
To: Noah Watkins <noahwatkins@...il.com>
cc: ceph-devel@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ceph: use kernel DNS resolver
Hey Noah,
On Thu, 22 Sep 2011, Noah Watkins wrote:
> 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.
Currently the dns resolution is handled by mount.ceph and 'rbd map/unmap'.
I don't think that will go away (at the very least need to support old
kernels).
Allowing this in the raw kernel interface would be nice, but I don't think
we want make DNS_RESOLVER a strict dependency, since it's new, kind of
kludgey, and a ripe target for compiling out of small or secure kernels.
Can you make it build either with or without it?
Thanks!
sage
>
> Signed-off-by: Noah Watkins <noahwatkins@...il.com>
> ---
> net/ceph/Kconfig | 1 +
> net/ceph/messenger.c | 106 ++++++++++++++++++++++++++++++++++++++++++++------
> 2 files changed, 95 insertions(+), 12 deletions(-)
>
> diff --git a/net/ceph/Kconfig b/net/ceph/Kconfig
> index be683f2..aac5fc8 100644
> --- a/net/ceph/Kconfig
> +++ b/net/ceph/Kconfig
> @@ -5,6 +5,7 @@ config CEPH_LIB
> select CRYPTO_AES
> select CRYPTO
> select KEYS
> + select DNS_RESOLVER
> default n
> help
> Choose Y or M here to include cephlib, which provides the
> diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
> index c340e2e..c22aa58 100644
> --- 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>
> @@ -1078,6 +1079,93 @@ 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.
> + */
> +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;
> +}
> +
> +/*
> + * 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 +1173,13 @@ 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 +1188,11 @@ 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 +1237,7 @@ 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);
>
> --
> 1.7.6.1
> --
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