Patchwork uClibc: make mDNS addresses resolvable via avahi daemon

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Submitter Voss, Nikolaus
Date March 30, 2012, 5:47 a.m.
Message ID <201203300601.q2U61G4l019973@gatekeeper.vosshq.de>
Download mbox | patch
Permalink /patch/149538/
State Rejected
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Comments

Voss, Nikolaus - March 30, 2012, 5:47 a.m.
If a uClibc toolchain is build and buildroot has avahi enabled,
currently avahi must be contacted directly to resolve mdns addresses.

This patch enables the uClibc resolver to contact avahi, so
mDNS addresses become resolvable by using libc calls. To enable
this feature in uClibC, UCLIBC_HAS_AVAHI_RES must be enabled in
uClibc configuration
---
 toolchain/uClibc/uClibc-0.9.33-avahi.patch |  418 ++++++++++++++++++++++++++++
 1 files changed, 418 insertions(+), 0 deletions(-)
 create mode 100644 toolchain/uClibc/uClibc-0.9.33-avahi.patch
Thomas Petazzoni - July 19, 2012, 9:10 p.m.
Hello Nikolaus,

Le Fri, 30 Mar 2012 07:47:42 +0200,
Nikolaus Voss <n.voss@weinmann.de> a écrit :

> If a uClibc toolchain is build and buildroot has avahi enabled,
> currently avahi must be contacted directly to resolve mdns addresses.
> 
> This patch enables the uClibc resolver to contact avahi, so
> mDNS addresses become resolvable by using libc calls. To enable
> this feature in uClibC, UCLIBC_HAS_AVAHI_RES must be enabled in
> uClibc configuration
> ---
>  toolchain/uClibc/uClibc-0.9.33-avahi.patch |  418 ++++++++++++++++++++++++++++
>  1 files changed, 418 insertions(+), 0 deletions(-)
>  create mode 100644 toolchain/uClibc/uClibc-0.9.33-avahi.patch

Thanks for this work. However, in Buildroot, we do not accept to carry
patches adding features to the different packages we have. We accept to
carry bug fixes or build fixes, but not entirely new features. For
these, we encourage people to get the features merged in the
respective upstream projects instead.

This allows us to avoid turning Buildroot into a big pile of
unmaintainable patches, which would prevent us from easily bumping
component versions. For example, once uClibc 0.9.34 is out, who will be
responsible for forward-porting such a large patch?

So please submit this to the uClibc community instead. While it gets
accepted, you can always add the patch to your local branch of
Buildroot.

Thanks again for contributing!

Thomas

Patch

diff --git a/toolchain/uClibc/uClibc-0.9.33-avahi.patch b/toolchain/uClibc/uClibc-0.9.33-avahi.patch
new file mode 100644
index 0000000..017ac5f
--- /dev/null
+++ b/toolchain/uClibc/uClibc-0.9.33-avahi.patch
@@ -0,0 +1,418 @@ 
+From 5654318b39dae5e5a32e290849ec590cb85ee0b3 Mon Sep 17 00:00:00 2001
+Message-Id: <5654318b39dae5e5a32e290849ec590cb85ee0b3.1322557154.git.n.voss@weinmann.de>
+In-Reply-To: <cover.1322557154.git.n.voss@weinmann.de>
+References: <cover.1322557154.git.n.voss@weinmann.de>
+From: Nikolaus Voss <n.voss@weinmann.de>
+Date: Mon, 28 Nov 2011 16:18:30 +0100
+Subject: [PATCH 1/2] gethostbyaddr_r: add space for alias pointers
+To: uclibc@uclibc.org
+
+addr_list and alias where on the same buffer offset. This led
+to corrupt addr_list which was overwritten by the resolved name.
+
+Signed-off-by: Nikolaus Voss <n.voss@weinmann.de>
+---
+ libc/inet/resolv.c |    2 ++
+ 1 files changed, 2 insertions(+), 0 deletions(-)
+
+diff --git a/libc/inet/resolv.c b/libc/inet/resolv.c
+index 021d5bf..bc596b0 100644
+--- a/libc/inet/resolv.c
++++ b/libc/inet/resolv.c
+@@ -2402,6 +2402,8 @@ int gethostbyaddr_r(const void *addr, socklen_t addrlen,
+ 	 */
+ #define in6 ((struct in6_addr *)in)
+ 	alias = (char **)buf;
++	buf += sizeof(alias) * 2;
++	buflen -= sizeof(alias) * 2;
+ 	addr_list = (struct in_addr**)buf;
+ 	buf += sizeof(*addr_list) * 2;
+ 	buflen -= sizeof(*addr_list) * 2;
+-- 
+1.7.5.4
+
+From 5388e302e40b12fb6682899dd4206f3e3d7a84fa Mon Sep 17 00:00:00 2001
+Message-Id: <5388e302e40b12fb6682899dd4206f3e3d7a84fa.1322557154.git.n.voss@weinmann.de>
+In-Reply-To: <cover.1322557154.git.n.voss@weinmann.de>
+References: <cover.1322557154.git.n.voss@weinmann.de>
+From: Nikolaus Voss <n.voss@weinmann.de>
+Date: Mon, 28 Nov 2011 16:22:42 +0100
+Subject: [PATCH 2/2] Make link-local addresses resolvable via running
+ avahi-daemon
+To: uclibc@uclibc.org
+
+nss-mdns is an extension to glibc to support resolution of link-local
+(.local) addresses via GNU Name Service Switch (NSS) which redirects
+the queries to a running avahi-daemon, which in turn does the resolution
+via multicast DNS (mdns).
+
+However, this does not work for uClibc, as it does not support NSS.
+
+This patch integrates the nss-mdns approach into uClibc's resolver,
+so getaddrinfo() and getnameinfo() calls get redirected to a running
+avahi-daemon before trying to resolve via unicast DNS.
+
+This increases the size of the library by 50 bytes on ARM.
+
+Signed-off-by: Nikolaus Voss <n.voss@weinmann.de>
+---
+ extra/Configs/Config.in                          |   19 +++
+ libc/inet/Makefile.in                            |    1 +
+ libc/inet/avahi.c                                |  183 ++++++++++++++++++++++
+ libc/inet/avahi.h                                |   33 ++++
+ libc/inet/resolv.c                               |   23 +++-
+ libc/sysdeps/linux/common/bits/kernel-features.h |    7 +-
+ 6 files changed, 259 insertions(+), 7 deletions(-)
+ create mode 100644 libc/inet/avahi.c
+ create mode 100644 libc/inet/avahi.h
+
+diff --git a/extra/Configs/Config.in b/extra/Configs/Config.in
+index e41adc4..6053a55 100644
+--- a/extra/Configs/Config.in
++++ b/extra/Configs/Config.in
+@@ -1268,6 +1268,25 @@ config UCLIBC_HAS_EXTRA_COMPAT_RES_STATE
+ 	  Answer Y if selecting UCLIBC_HAS_COMPAT_RES_STATE is not enough.
+ 	  As far as I can say, this should never be needed.
+ 
++config UCLIBC_HAS_AVAHI_RES
++	bool "Try to resolve link-local IP addresses via avahi-daemon"
++	default n
++	depends on UCLIBC_HAS_IPV4 || UCLIBC_HAS_IPV6
++	help
++	  Answer Y if you want to resolve .local addresses via multicast-dns.
++	  The queries are forwarded to a running avahi-daemon via a domain
++	  socket interface.
++	  Note that this might interfere with a .local domain on your DNS.
++	  Answering N saves around 50 bytes.
++
++config UCLIBC_AVAHI_SOCKET_PATH
++	string "Path to avahi unix domain socket"
++	default "/var/run/avahi-daemon/socket"
++	depends on UCLIBC_HAS_AVAHI_RES
++	help
++	  A running avahi-daemon creates a socket to listen for queries.
++	  Enter the path you configured your avahi-daemon to.
++
+ config UCLIBC_HAS_LIBRESOLV_STUB
+ 	bool "Provide libresolv stub"
+ 	default n
+diff --git a/libc/inet/Makefile.in b/libc/inet/Makefile.in
+index d588220..7f436c9 100644
+--- a/libc/inet/Makefile.in
++++ b/libc/inet/Makefile.in
+@@ -33,6 +33,7 @@ CSRC-$(findstring y,$(UCLIBC_HAS_IPV4)$(UCLIBC_HAS_IPV6)) += \
+ 	dnslookup.c opennameservers.c closenameservers.c \
+ 	getnameinfo.c \
+ 	gethostent.c gethostent_r.c
++CSRC-$(UCLIBC_HAS_AVAHI_RES) += avahi.c
+ CSRC-$(findstring y,$(UCLIBC_HAS_IPV4)$(UCLIBC_HAS_IPV6)) += \
+ 	get_hosts_byaddr_r.c get_hosts_byname_r.c \
+ 	gethostbyaddr_r.c gethostbyname_r.c gethostbyname2_r.c \
+diff --git a/libc/inet/avahi.c b/libc/inet/avahi.c
+new file mode 100644
+index 0000000..11ce055
+--- /dev/null
++++ b/libc/inet/avahi.c
+@@ -0,0 +1,183 @@
++/*
++ *
++ * (C) 2011 Weinmann GmbH, Hamburg, Germany
++ *
++ * Author: Nikolaus Voss <n.voss@weinmann.de>
++ *
++ * Derived from avahi.c / nss-mdns by Lennart Poettering.
++ * Copyright 2004-2007 Lennart Poettering <mzaffzqaf (at) 0pointer (dot) de>
++ *
++ * Licensed under the LGPL v2.1, see the file COPYING.LIB in this tarball.
++ *
++ */
++
++#include <arpa/inet.h>
++#include <fcntl.h>
++#include <not-cancel.h>
++#include <stdio.h>
++#include <string.h>
++#include <sys/socket.h>
++#include <sys/types.h>
++#include <sys/un.h>
++#include <unistd.h>
++
++#include "avahi.h"
++
++#define WHITESPACE " \t"
++
++static FILE *avahi_open_socket(void)
++{
++	int fd;
++	struct sockaddr_un sa;
++	FILE *f;
++
++	fd = socket(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0);
++
++	if (fd < 0)
++		return NULL;
++
++#ifndef __ASSUME_SOCK_CLOEXEC
++	fcntl_not_cancel(fd, F_SETFD, FD_CLOEXEC);
++#endif
++
++	memset(&sa, 0, sizeof(sa));
++	sa.sun_family = AF_UNIX;
++	strncpy(sa.sun_path, __UCLIBC_AVAHI_SOCKET_PATH__,
++		sizeof(sa.sun_path) - 1);
++	sa.sun_path[sizeof(sa.sun_path) - 1] = 0;
++
++	if (connect(fd, (struct sockaddr *) &sa, sizeof(sa)) < 0)
++		goto fail;
++
++	f = fdopen(fd, "r+");
++	if (!f)
++		goto fail;
++
++	return f;
++
++fail:
++	close(fd);
++
++	return NULL;
++}
++
++static int avahi_ends_with(const char *name, const char* suffix)
++{
++	size_t ln, ls;
++
++	if (!name || !suffix)
++		return 0;
++
++	if ((ls = strlen(suffix)) > (ln = strlen(name)))
++		return 0;
++
++	return strcasecmp(name + ln - ls, suffix) == 0;
++}
++
++int __avahi_resolve_name(int af, const char* name, void* data)
++{
++	FILE *f;
++	char *p;
++	int ret = -1;
++	char ln[256];
++
++	if (af != AF_INET && af != AF_INET6)
++		return ret;
++
++	if (!avahi_ends_with(name, ".local") &&
++	    !avahi_ends_with(name, ".local."))
++		return ret;
++
++	f = avahi_open_socket();
++	if (!f)
++		return ret;
++
++	fprintf(f, "RESOLVE-HOSTNAME-IPV%d %s\n", af == AF_INET ? 4 : 6, name);
++	fflush(f);
++
++	if (!fgets(ln, sizeof(ln), f))
++		goto finish;
++
++	if (ln[0] != '+') {
++		ret = 1;
++		goto finish;
++	}
++
++	p = ln + 1;
++	p += strspn(p, WHITESPACE);
++
++	/* Skip interface */
++	p += strcspn(p, WHITESPACE);
++	p += strspn(p, WHITESPACE);
++
++	/* Skip protocol */
++	p += strcspn(p, WHITESPACE);
++	p += strspn(p, WHITESPACE);
++
++	/* Skip host name */
++	p += strcspn(p, WHITESPACE);
++	p += strspn(p, WHITESPACE);
++
++	/* Cut off end of line */
++	p[strcspn(p, "\n\r\t ")] = 0;
++
++	if (inet_pton(af, p, data) <= 0)
++		goto finish;
++
++	ret = 0;
++
++finish:
++	fclose(f);
++
++	return ret;
++}
++
++int __avahi_resolve_address(int af, const void *data, char* name,
++			    size_t name_len)
++{
++	FILE *f;
++	char *p;
++	int ret = -1;
++	char a[256], ln[256];
++
++	if (af != AF_INET && af != AF_INET6)
++		return ret;
++
++	f = avahi_open_socket();
++	if (!f)
++		return ret;
++
++	fprintf(f, "RESOLVE-ADDRESS %s\n", inet_ntop(af, data, a, sizeof(a)));
++
++	if (!fgets(ln, sizeof(ln), f))
++		goto finish;
++
++	if (ln[0] != '+') {
++		ret = 1;
++		goto finish;
++	}
++
++	p = ln + 1;
++	p += strspn(p, WHITESPACE);
++
++	/* Skip interface */
++	p += strcspn(p, WHITESPACE);
++	p += strspn(p, WHITESPACE);
++
++	/* Skip protocol */
++	p += strcspn(p, WHITESPACE);
++	p += strspn(p, WHITESPACE);
++
++	/* Cut off end of line */
++	p[strcspn(p, "\n\r\t ")] = 0;
++
++	strncpy(name, p, name_len - 1);
++	name[name_len - 1] = 0;
++
++	ret = 0;
++
++finish:
++	fclose(f);
++
++	return ret;
++}
+diff --git a/libc/inet/avahi.h b/libc/inet/avahi.h
+new file mode 100644
+index 0000000..85df5f6
+--- /dev/null
++++ b/libc/inet/avahi.h
+@@ -0,0 +1,33 @@
++/*
++ *
++ * (C) 2011 Weinmann GmbH, Hamburg, Germany
++ *
++ * Author: Nikolaus Voss <n.voss@weinmann.de>
++ *
++ * Licensed under the LGPL v2.1, see the file COPYING.LIB in this tarball.
++ *
++ */
++
++#ifndef _UCLIBC_AVAHI_H_
++#define _UCLIBC_AVAHI_H_
++
++#ifdef __UCLIBC_HAS_AVAHI_RES__
++int __avahi_resolve_name(int af, const char* name, void* data) attribute_hidden;
++
++int __avahi_resolve_address(int af, const void *data, char* name,
++			    size_t name_len) attribute_hidden;
++#else
++static inline int __avahi_resolve_name(int af, const char* name, void* data)
++	attribute_hidden
++{
++	return 1;
++}
++
++static inline int __avahi_resolve_address(int af, const void *data, char* name,
++					  size_t name_len) attribute_hidden
++{
++	return 1;
++}
++#endif
++
++#endif
+diff --git a/libc/inet/resolv.c b/libc/inet/resolv.c
+index bc596b0..2527b50 100644
+--- a/libc/inet/resolv.c
++++ b/libc/inet/resolv.c
+@@ -318,6 +318,7 @@ Domain name in a message can be represented as either:
+ #include <sys/stat.h>
+ #include <bits/uClibc_mutex.h>
+ #include "internal/parse_config.h"
++#include "avahi.h"
+ 
+ /* poll() is not supported in kernel <= 2.0, therefore if __NR_poll is
+  * not available, we assume an old Linux kernel is in use and we will
+@@ -2073,10 +2074,11 @@ int gethostbyname_r(const char *name,
+ 	alias[0] = alias0;
+ 	alias[1] = NULL;
+ 
+-	/* maybe it is already an address? */
++	/* maybe it is resolvable via avahi or already an address? */
+ 	{
+ 		struct in_addr *in = (struct in_addr *)(buf + sizeof(addr_list[0]) * 2);
+-		if (inet_aton(name, in)) {
++		if (!__avahi_resolve_name(AF_INET, name, in) ||
++		    inet_aton(name, in)) {
+ 			addr_list[0] = in;
+ 			addr_list[1] = NULL;
+ 			result_buf->h_name = alias0;
+@@ -2263,8 +2265,9 @@ int gethostbyname2_r(const char *name,
+ 	strncpy(buf, name, buflen);
+ 	buf[buflen] = '\0';
+ 
+-	/* maybe it is already an address? */
+-	if (inet_pton(AF_INET6, name, in)) {
++	/* maybe it is resolvable via avahi or already an address? */
++	if (!__avahi_resolve_name(AF_INET6, name, in) ||
++	    inet_pton(AF_INET6, name, in)) {
+ 		result_buf->h_name = buf;
+ 		result_buf->h_addrtype = AF_INET6;
+ 		result_buf->h_length = sizeof(*in);
+@@ -2427,6 +2430,18 @@ int gethostbyaddr_r(const void *addr, socklen_t addrlen,
+ 	addr_list[1] = NULL;
+ 	memcpy(in, addr, addrlen);
+ 
++	/* is this a .local address? */
++	if (!__avahi_resolve_address(type, in, buf, buflen)) {
++		result_buf->h_name = buf;
++		result_buf->h_addrtype = type;
++		result_buf->h_length = addrlen;
++		result_buf->h_addr_list = (char **) addr_list;
++		result_buf->h_aliases = alias;
++		*result = result_buf;
++		*h_errnop = NETDB_SUCCESS;
++		return NETDB_SUCCESS;
++	}
++
+ 	if (0) /* nothing */;
+ #ifdef __UCLIBC_HAS_IPV4__
+ 	else IF_HAS_BOTH(if (type == AF_INET)) {
+diff --git a/libc/sysdeps/linux/common/bits/kernel-features.h b/libc/sysdeps/linux/common/bits/kernel-features.h
+index 6bf5544..a322334 100644
+--- a/libc/sysdeps/linux/common/bits/kernel-features.h
++++ b/libc/sysdeps/linux/common/bits/kernel-features.h
+@@ -310,11 +310,12 @@
+ #endif
+ 
+ /* Support for various CLOEXEC and NONBLOCK flags was added for x86,
+- *    x86-64, PPC, IA-64, and SPARC in 2.6.27.  */
++ *    x86-64, PPC, IA-64, ARM and SPARC in 2.6.27.  */
+ #if __LINUX_KERNEL_VERSION >= 0x02061b \
+     && (defined __i386__ || defined __x86_64__ || defined __powerpc__ \
+-        || defined __ia64__ || defined __sparc__ || defined __s390__)
+-/* # define __ASSUME_SOCK_CLOEXEC  1 */
++        || defined __ia64__ || defined __sparc__ || defined __s390__ \
++        || defined __arm__)
++# define __ASSUME_SOCK_CLOEXEC  1
+ /* # define __ASSUME_IN_NONBLOCK   1 */
+ # define __ASSUME_PIPE2         1
+ /* # define __ASSUME_EVENTFD2      1 */
+-- 
+1.7.5.4
+