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On 08/04/2009 03:48 PM, Jakub Hrozek wrote:
> On 08/03/2009 01:57 PM, Daniel Stenberg wrote:
>> Sorry for the delay. I am interested in getting this merged. I'm just
>> swamped with work and I need (more) help with c-ares.
>
>
> No problem :-)
>
>> In this version of the patch, won't we risk reading a 16bit word from an
>> un-aligned memory address? I can't see how 'aptr' is guranteed to be
>> aligned when you do *(uint16_t *) reads from it and that will crash on
>> numerous architectures. Or am I wrong?
>
> I think you are right, I did not think about memory alignment. IIRC
> using memcpy as I did in the previous iteration should take care of
> these issues, right?
>
> I also wrote a short manpage for the parse function as I've noticed that
> it was the only one without it. If there are no other concerns I can
> resend another patch.
>
> Thank you for the review!
> Jakub
>
Patch against CVS HEAD attached.
Thanks,
Jakub
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diff -up ./ares.h.srv ./ares.h
--- ./ares.h.srv 2009-08-04 11:53:38.000000000 +0200
+++ ./ares.h 2009-08-04 11:51:25.000000000 +0200
@@ -322,6 +322,13 @@ struct addr6ttl {
int ttl;
};
+struct srv_reply {
+ u_int16_t weight;
+ u_int16_t priority;
+ u_int16_t port;
+ char *host;
+};
+
/*
** Parse the buffer, starting at *abuf and of length alen bytes, previously
** obtained from an ares_search call. Put the results in *host, if nonnull.
@@ -339,6 +346,8 @@ int ares_parse_ptr_reply(const unsigned
int addrlen, int family, struct hostent **host);
int ares_parse_ns_reply(const unsigned char *abuf, int alen,
struct hostent **host);
+int ares_parse_srv_reply(const unsigned char* abuf, int alen,
+ struct srv_reply** srv_out, int *nsrvreply);
void ares_free_string(void *str);
void ares_free_hostent(struct hostent *host);
const char *ares_strerror(int code);
diff -up ./ares_parse_srv_reply.3.srv ./ares_parse_srv_reply.3
--- ./ares_parse_srv_reply.3.srv 2009-08-04 11:15:44.000000000 +0200
+++ ./ares_parse_srv_reply.3 2009-08-04 11:45:58.000000000 +0200
@@ -0,0 +1,78 @@
+.\"
+.\" Copyright 1998 by the Massachusetts Institute of Technology.
+.\"
+.\" Permission to use, copy, modify, and distribute this
+.\" software and its documentation for any purpose and without
+.\" fee is hereby granted, provided that the above copyright
+.\" notice appear in all copies and that both that copyright
+.\" notice and this permission notice appear in supporting
+.\" documentation, and that the name of M.I.T. not be used in
+.\" advertising or publicity pertaining to distribution of the
+.\" software without specific, written prior permission.
+.\" M.I.T. makes no representations about the suitability of
+.\" this software for any purpose. It is provided "as is"
+.\" without express or implied warranty.
+.\"
+.TH ARES_PARSE_SRV_REPLY 3 "4 August 2009"
+.SH NAME
+ares_parse_srv_reply \- Parse a reply to a DNS query of type SRV into a
+struct srv_reply
+.SH SYNOPSIS
+.nf
+.B #include <ares.h>
+.PP
+.B int ares_parse_srv_reply(const unsigned char* \fIabuf\fP, int \fIalen\fP,
+.B struct srv_reply** \fIsrv_out\fP, int *\fInsrvreply\fP);
+.fi
+.SH DESCRIPTION
+The
+.B ares_parse_srv_reply
+function parses the response to a query of type SRV into a
+.I struct srv_reply
+The parameters
+.I abuf
+and
+.I alen
+give the contents of the response. The result is stored in allocated
+memory and a pointer to it stored into the variable pointed to by
+.IR srv_out .
+The number of responses is stored into the variable pointed to by
+.IR nsrvreply .
+It is the caller's responsibility to free the resulting
+.IR srv_out
+structure when it is no longer needed.
+.PP
+The structure
+.I srv_reply
+contains the following fields:
+.sp
+.in +4n
+.nf
+struct srv_reply {
+ u_int16_t weight;
+ u_int16_t priority;
+ u_int16_t port;
+ char *host;
+};
+.fi
+.in
+.PP
+.SH RETURN VALUES
+.B ares_parse_srv_reply
+can return any of the following values:
+.TP 15
+.B ARES_SUCCESS
+The response was successfully parsed.
+.TP 15
+.B ARES_EBADRESP
+The response was malformatted.
+.TP 15
+.B ARES_ENODATA
+The response did not contain an answer to the query.
+.TP 15
+.B ARES_ENOMEM
+Memory was exhausted.
+.SH SEE ALSO
+.BR ares_query (3)
+.SH AUTHOR
+Written by Jakub Hrozek <jhro...@redhat.com>, on behalf of Red Hat, Inc http://www.redhat.com
diff -up ./ares_parse_srv_reply.c.srv ./ares_parse_srv_reply.c
--- ./ares_parse_srv_reply.c.srv 2009-07-02 14:27:57.000000000 +0200
+++ ./ares_parse_srv_reply.c 2009-07-15 12:59:59.000000000 +0200
@@ -0,0 +1,159 @@
+/* Copyright 1998 by the Massachusetts Institute of Technology.
+ *
+ * Permission to use, copy, modify, and distribute this
+ * software and its documentation for any purpose and without
+ * fee is hereby granted, provided that the above copyright
+ * notice appear in all copies and that both that copyright
+ * notice and this permission notice appear in supporting
+ * documentation, and that the name of M.I.T. not be used in
+ * advertising or publicity pertaining to distribution of the
+ * software without specific, written prior permission.
+ * M.I.T. makes no representations about the suitability of
+ * this software for any purpose. It is provided "as is"
+ * without express or implied warranty.
+ */
+
+/*
+ * ares_parse_srv_reply created by Jakub Hrozek <jhro...@redhat.com>
+ * on behalf of Red Hat - http://www.redhat.com
+ */
+
+#include "setup.h"
+
+#if defined(WIN32) && !defined(WATT32)
+#include "nameser.h"
+#else
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <netdb.h>
+#include <arpa/nameser.h>
+#ifdef HAVE_ARPA_NAMESER_COMPAT_H
+#include <arpa/nameser_compat.h>
+#endif
+#endif
+
+#include <stdlib.h>
+#include <string.h>
+#include "ares.h"
+#include "ares_dns.h"
+#include "ares_private.h"
+
+int
+ares_parse_srv_reply (const unsigned char *abuf, int alen,
+ struct srv_reply **srv_out, int *nsrvreply)
+{
+ unsigned int qdcount, ancount;
+ const unsigned char *aptr;
+ int status, i, rr_type, rr_class, rr_len;
+ long len;
+ char *hostname = NULL, *rr_name = NULL;
+ struct srv_reply *srv = NULL;
+
+ /* Set *srv_out to NULL for all failure cases. */
+ if (srv_out)
+ *srv_out = NULL;
+ /* Same with *nsrvreply. */
+ if (nsrvreply)
+ *nsrvreply = 0;
+
+ /* Give up if abuf doesn't have room for a header. */
+ if (alen < HFIXEDSZ)
+ return ARES_EBADRESP;
+
+ /* Fetch the question and answer count from the header. */
+ qdcount = DNS_HEADER_QDCOUNT (abuf);
+ ancount = DNS_HEADER_ANCOUNT (abuf);
+ if (qdcount != 1)
+ return ARES_EBADRESP;
+ if (ancount == 0)
+ return ARES_ENODATA;
+
+ /* Expand the name from the question, and skip past the question. */
+ aptr = abuf + HFIXEDSZ;
+ status = ares_expand_name (aptr, abuf, alen, &hostname, &len);
+ if (status != ARES_SUCCESS)
+ return status;
+
+ if (aptr + len + QFIXEDSZ > abuf + alen)
+ {
+ free (hostname);
+ return ARES_EBADRESP;
+ }
+ aptr += len + QFIXEDSZ;
+
+ /* Allocate srv_reply array; ancount gives an upper bound */
+ srv = malloc ((ancount) * sizeof (struct srv_reply));
+ if (!srv)
+ {
+ free (hostname);
+ return ARES_ENOMEM;
+ }
+
+ /* Examine each answer resource record (RR) in turn. */
+ for (i = 0; i < (int) ancount; i++)
+ {
+ /* Decode the RR up to the data field. */
+ status = ares_expand_name (aptr, abuf, alen, &rr_name, &len);
+ if (status != ARES_SUCCESS)
+ {
+ break;
+ }
+ aptr += len;
+ if (aptr + RRFIXEDSZ > abuf + alen)
+ {
+ status = ARES_EBADRESP;
+ break;
+ }
+ rr_type = DNS_RR_TYPE (aptr);
+ rr_class = DNS_RR_CLASS (aptr);
+ rr_len = DNS_RR_LEN (aptr);
+ aptr += RRFIXEDSZ;
+
+ /* Check if we are really looking at a SRV record */
+ if (rr_class == C_IN && rr_type == T_SRV)
+ {
+ /* parse the SRV record itself */
+ if (rr_len < 6)
+ {
+ status = ARES_EBADRESP;
+ break;
+ }
+
+ srv[i].priority = ntohs (*((uint16_t *)aptr));
+ aptr += sizeof(uint16_t);
+ srv[i].weight = ntohs (*((uint16_t *)aptr));
+ aptr += sizeof(uint16_t);
+ srv[i].port = ntohs (*((uint16_t *)aptr));
+ aptr += sizeof(uint16_t);
+
+ status = ares_expand_name (aptr, abuf, alen, &srv[i].host, &len);
+ if (status != ARES_SUCCESS)
+ break;
+
+ /* Move on to the next record */
+ aptr += len;
+
+ /* Don't lose memory in the next iteration */
+ free (rr_name);
+ rr_name = NULL;
+ }
+ }
+
+ /* clean up on error */
+ if (status != ARES_SUCCESS)
+ {
+ free (srv);
+ free (hostname);
+ free (rr_name);
+ return status;
+ }
+
+ /* everything looks fine, return the data */
+ *srv_out = srv;
+ *nsrvreply = ancount;
+
+ free (hostname);
+ free (rr_name);
+ return status;
+}
diff -up ./Makefile.inc.srv ./Makefile.inc
--- ./Makefile.inc.srv 2009-07-01 18:05:45.000000000 +0200
+++ ./Makefile.inc 2009-07-02 13:52:44.000000000 +0200
@@ -22,6 +22,7 @@ CSOURCES = ares__close_sockets.c \
ares_parse_aaaa_reply.c \
ares_parse_ns_reply.c \
ares_parse_ptr_reply.c \
+ ares_parse_srv_reply.c \
ares_process.c \
ares_query.c \
ares_search.c \
