> On Aug 18, 2016, at 2:37 PM, Steve Dickson <SteveD@xxxxxxxxxx> wrote:
>
> In domain_from_dns(), when at the hostname is a FQHN
> query the DNS server for the _nfsv4idmapdomain TXT
> record. If the record exists, use that as the
> NFSv4 domain.
>
> Note, this query will only happen if the domain name
> is not set in the /etc/idmapd.conf
>
> Signed-off-by: Steve Dickson <steved@xxxxxxxxxx>
All three:
Reviewed-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> ---
> libnfsidmap.c | 104 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 103 insertions(+), 1 deletion(-)
>
> diff --git a/libnfsidmap.c b/libnfsidmap.c
> index 2db4d13..7b8c0ed 100644
> --- a/libnfsidmap.c
> +++ b/libnfsidmap.c
> @@ -53,6 +53,10 @@
> #include <stdarg.h>
> #include <dlfcn.h>
> #include <ctype.h>
> +#include <resolv.h>
> +#include <arpa/nameser.h>
> +#include <arpa/nameser_compat.h>
> +
> #include "nfsidmap.h"
> #include "nfsidmap_internal.h"
> #include "cfg.h"
> @@ -79,6 +83,11 @@ gid_t nobody_gid = (gid_t)-1;
> #define IDMAPD_DEFAULT_DOMAIN "localdomain"
> #endif
>
> +#ifndef NFS4DNSTXTREC
> +#define NFS4DNSTXTREC "_nfsv4idmapdomain"
> +#endif
> +
> +
> /* Default logging fuction */
> static void default_logger(const char *fmt, ...)
> {
> @@ -114,6 +123,93 @@ static int id_as_chars(char *name, uid_t *id)
> return 1;
> }
>
> +static int dns_txt_query(char *domain, char **nfs4domain)
> +{
> + char *txtname = NFS4DNSTXTREC;
> + char *msg, *answ, *eom, *mptr;
> + int len, status = -1;
> + HEADER *hdr;
> +
> + msg = calloc(1, NS_MAXMSG);
> + if (msg == NULL)
> + return -1;
> +
> + answ = calloc(1, NS_MAXMSG);
> + if (answ == NULL) {
> + free(msg);
> + return -1;
> + }
> +
> + if (res_init() < 0) {
> + IDMAP_LOG(2, ("libnfsidmap: res_init() failed for %s.%s: %s\n",
> + txtname, domain, hstrerror(h_errno)));
> + goto freemem;
> + }
> + len = res_querydomain(txtname, domain, C_IN, T_TXT, msg, NS_MAXMSG);
> + if (len < 0) {
> + IDMAP_LOG(2, ("libnfsidmap: res_querydomain() failed for %s.%s: %s\n",
> + txtname, domain, hstrerror(h_errno)));
> + goto freemem;
> + }
> + hdr = (HEADER *)msg;
> +
> + /* See if there is an answer */
> + if (ntohs(hdr->ancount) < 1) {
> + IDMAP_LOG(2, ("libnfsidmap: No TXT record for %s.%s\n",
> + txtname, domain));
> + goto freemem;
> + }
> + /* find the EndOfMessage */
> + eom = msg + len;
> +
> + /* skip header */
> + mptr = &msg[HFIXEDSZ];
> +
> + /* skip name field in question section */
> + mptr += dn_skipname(mptr, eom) + QFIXEDSZ;
> +
> + /* read in the question */
> + len = dn_expand(msg, eom, mptr, answ, NS_MAXDNAME);
> + if (len < 0) { /* does this really matter?? */
> + IDMAP_LOG(2, ("libnfsidmap: No question section for %s.%s: %s\n",
> + txtname, domain, hstrerror(h_errno)));
> + goto freemem;
> + }
> +
> + /*
> + * Now, dissect the answer section, Note: if there
> + * are more than one answer only the first
> + * one will be used.
> + */
> +
> + /* skip passed the name field */
> + mptr += dn_skipname(mptr, eom);
> + /* skip pass the type class and ttl fields */
> + mptr += 2 + 2 + 4;
> +
> + /* make sure there is some data */
> + GETSHORT(len, mptr);
> + if (len < 0) {
> + IDMAP_LOG(2, ("libnfsidmap: No data in answer for %s.%s\n",
> + txtname, domain));
> + goto freemem;
> + }
> + /* get the lenght field */
> + len = (int)*mptr++;
> + /* copy the data */
> + memcpy(answ, mptr, len);
> + answ[len] = '\0';
> +
> + *nfs4domain = strdup(answ);
> + status = 0;
> +
> +freemem:
> + free(msg);
> + free(answ);
> +
> + return (status);
> +}
> +
> static int domain_from_dns(char **domain)
> {
> struct hostent *he;
> @@ -125,7 +221,13 @@ static int domain_from_dns(char **domain)
> return -1;
> if ((c = strchr(he->h_name, '.')) == NULL || *++c == '\0')
> return -1;
> - *domain = strdup(c);
> + /*
> + * Query DNS to see if the _nfsv4idmapdomain TXT record exists
> + * If so use it...
> + */
> + if (dns_txt_query(c, domain) < 0)
> + *domain = strdup(c);
> +
> return 0;
> }
>
> --
> 2.7.4
>
> --
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--
Chuck Lever
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