From 5a62c294114083df5ac4759e8bda232efdf3e025 Mon Sep 17 00:00:00 2001 From: Lennart Poettering Date: Sun, 15 May 2005 17:06:08 +0000 Subject: * send "legacy unicast" packets instead of normal mDNS packets * prepare for release 0.4 git-svn-id: file:///home/lennart/svn/public/nss-mdns/trunk@75 0ee8848e-81ea-0310-a63a-f631d1a40d77 --- configure.ac | 2 +- doc/README.html.in | 45 +++++++++------- src/dns.c | 5 +- src/mdns-test.c | 8 +-- src/query.c | 154 +++++++++++++++++++++++++++++++++-------------------- 5 files changed, 129 insertions(+), 85 deletions(-) diff --git a/configure.ac b/configure.ac index f15f54e..e8cc023 100644 --- a/configure.ac +++ b/configure.ac @@ -21,7 +21,7 @@ # USA. AC_PREREQ(2.57) -AC_INIT([nss-mdns],[0.3],[mzaffzqaf (at) 0pointer (dot) de]) +AC_INIT([nss-mdns],[0.4],[mzaffzqaf (at) 0pointer (dot) de]) AC_CONFIG_SRCDIR([src/query.c]) AC_CONFIG_HEADERS([config.h]) AM_INIT_AUTOMAKE([foreign -Wall]) diff --git a/doc/README.html.in b/doc/README.html.in index 65955d0..5dc131f 100644 --- a/doc/README.html.in +++ b/doc/README.html.in @@ -42,9 +42,15 @@ Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

News

+
Sun May 15 2005:

Version 0.4 +released. Changes include: small portability fix for big endian +architectures; send "legacy unicast" packets instead of normal mDNS +packets (this should reduce traffic and improve response time)

+
Jan Sun 16 2005:

Version 0.3 -released. Changes include: add Debianization, use ip6.arpa instead of ip6.int for reverse IPv6 lookups.

+released. Changes include: add Debianization; use ip6.arpa instead of ip6.int for reverse IPv6 lookups.

Fri Dec 17 2004:

Version 0.2 @@ -70,11 +76,12 @@ means that you have to run a mDNS responder daemon seperately from nss-mdns if you want to register the local host name via mDNS (e.g. HOWL).

-

nss-mdns is very lightweight (22 KByte stripped binary .so compiled with --DNDEBUG=1 on i386, gcc 3.3), has no dependencies besides the glibc and requires only minimal -configuration.

+

nss-mdns is very lightweight (23 KByte stripped binary +.so compiled with -DNDEBUG=1 on i386, gcc +3.3), has no dependencies besides the glibc and requires only +minimal configuration.

-

Status

+

Current Status

It works!

@@ -100,7 +107,8 @@ lookup for IPv4.

To activate one of the NSS modules you have to edit /etc/nsswitch.conf and add mdns4 -(resp. mdns, mdns6) to the line starting with "hosts:". On Debian this looks like this:

+(resp. mdns, mdns6) to the line starting with +"hosts:". On Debian this looks like this:

# /etc/nsswitch.conf
 
@@ -125,23 +133,24 @@ use glibc's getent tool:
 
$ getent hosts foo.local
 192.168.50.4    foo.local

 
-
Replace foo whith a host name that has been registered with an mDNS responder.

-
-
Due to some traffic suppression algorithms in mDNS responders
-repeated mDNS resolutions are slowed down. Consider installing glibc's name
-service cache daemon nscd to work around this limitation.

+
Replace foo whith a host name that has been registered with
+an mDNS responder.

 
-
When doing troubleshooting for nss-mdns, don't forget to
-disable nscd for getting sensible results.

+
To reduce the traffic nss-mdns is responsible for consider
+installing glibc's name service cache daemon
+nscd. However, when doing troubleshooting for
+nss-mdns, don't forget to disable nscd for getting
+sensible results.

 
-
If you run a firewall, don't forget to allow UDP traffic from and to port 5353
-from and to the the mDNS multicast address 224.0.0.251.

+
If you run a firewall, don't forget to allow UDP traffic to the the
+mDNS multicast address 224.0.0.251 on port 5353.

 
 
Requirements

 
-
Currently, nss-mdns is tested on Linux only. A fairly modern glibc installation with development headers (2.0 or newer) is required. Not
-suprisingly nss-mdns requires a kernel compiled with IPv4
-multicasting support enabled.

+
Currently, nss-mdns is tested on Linux only. A fairly
+modern glibc installation with development headers (2.0 or
+newer) is required. Not suprisingly nss-mdns requires a
+kernel compiled with IPv4 multicasting support enabled.

 
 
nss-mdns was developed and tested on Debian GNU/Linux
 "testing" from December 2004, it should work on most other Linux
diff --git a/src/dns.c b/src/dns.c
index c3be024..b32dc2f 100644
--- a/src/dns.c
+++ b/src/dns.c
@@ -157,9 +157,6 @@ int dns_packet_check_valid_response(struct dns_packet *p) {
     if (!(flags & DNS_FLAG_QR))
         return -1;
 
-    if (dns_packet_get_field(p, DNS_FIELD_QDCOUNT) > 0)
-        return -1;
-
     return 0;
     
 }
@@ -278,7 +275,7 @@ int dns_packet_consume_bytes(struct dns_packet *p, void *ret_data, size_t l) {
 }
 
 int dns_packet_consume_seek(struct dns_packet *p, size_t length) {
-    assert(p && length >= 0);
+    assert(p);
 
     if (!length)
         return 0;
diff --git a/src/mdns-test.c b/src/mdns-test.c
index c8fbdb9..e3c7981 100644
--- a/src/mdns-test.c
+++ b/src/mdns-test.c
@@ -47,10 +47,10 @@ int main(int argc, char *argv[]) {
     if ((fd = mdns_open_socket()) < 0)
         goto finish;
 
-/*     if (mdns_query_name(fd, argc > 1 ? argv[1] : "ecstasy.local", &ipv4_func, &ipv6_func, NULL) < 0) */
-/*         goto finish; */
-
-    ipv4.address = inet_addr(argc > 1 ? argv[1] : "192.168.100.1"); 
+    if (mdns_query_name(fd, argc > 1 ? argv[1] : "cocaine.local", &ipv4_func, &ipv6_func, NULL) < 0) 
+        goto finish;
+    
+    ipv4.address = inet_addr(argc > 1 ? argv[1] : "192.168.50.1");
     
     if (mdns_query_ipv4(fd, &ipv4, name_func, NULL) < 0) 
         goto finish; 
diff --git a/src/query.c b/src/query.c
index 546d072..1b66df9 100644
--- a/src/query.c
+++ b/src/query.c
@@ -36,15 +36,33 @@
 #include 
 #include 
 #include 
+#include 
 
 #include "dns.h"
 #include "util.h"
 #include "query.h"
 
-static const usec_t retry_ms[] = { 200000, 500000, 900000, 1400000, 0 };
+static const usec_t retry_ms[] = { 500000, 1000000, 0 };
+
+static uint16_t get_random_id(void) {
+    uint16_t id = 0;
+    int ok = 0, fd;
+    
+    if ((fd = open("/dev/urandom", O_RDONLY)) >= 0) {
+        ok = read(fd, &id, sizeof(id)) == 2;
+        close(fd);
+    }
+
+    if (!ok)
+        ok = random() & 0xFFFF;
+
+    return id;
+}
 
 static void mdns_mcast_group(struct sockaddr_in *ret_sa) {
     assert(ret_sa);
+
+    memset(ret_sa, 0, sizeof(struct sockaddr_in));
     
     ret_sa->sin_family = AF_INET;
     ret_sa->sin_port = htons(5353);
@@ -52,44 +70,30 @@ static void mdns_mcast_group(struct sockaddr_in *ret_sa) {
 }
 
 int mdns_open_socket(void) {
-    struct ip_mreqn mreq;
     struct sockaddr_in sa;
     int fd = -1, ttl, yes;
 
-    mdns_mcast_group(&sa);
-        
     if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
         fprintf(stderr, "socket() failed: %s\n", strerror(errno));
         goto fail;
     }
-    
+
     ttl = 255;
     if (setsockopt(fd, IPPROTO_IP, IP_MULTICAST_TTL, &ttl, sizeof(ttl)) < 0) {
         fprintf(stderr, "IP_MULTICAST_TTL failed: %s\n", strerror(errno));
         goto fail;
     }
 
-    yes = 1;
-    if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(yes)) < 0) {
-        fprintf(stderr, "SO_REUSEADDR failed: %s\n", strerror(errno));
-        goto fail;
-    }
-
+    sa.sin_family = AF_INET;
+    sa.sin_port = 0;
+    sa.sin_addr.s_addr = INADDR_ANY;
+    
     if (bind(fd, (struct sockaddr*) &sa, sizeof(sa)) < 0) {
         fprintf(stderr, "bind() failed: %s\n", strerror(errno));
         goto fail;
     }
-
-    memset(&mreq, 0, sizeof(mreq));
-    mreq.imr_multiaddr = sa.sin_addr;
-    mreq.imr_address.s_addr = htonl(INADDR_ANY);
-    mreq.imr_ifindex = 0;
     
-    if (setsockopt(fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) < 0) {
-        fprintf(stderr, "IP_ADD_MEMBERSHIP failed: %s\n", strerror(errno));
-        goto fail;
-    }
-
+    yes = 1;
     if (setsockopt(fd, IPPROTO_IP, IP_RECVTTL, &yes, sizeof(yes)) < 0) {
         fprintf(stderr, "IP_RECVTTL failed: %s\n", strerror(errno));
         goto fail;
@@ -284,7 +288,7 @@ fail:
     return ret;
 }
 
-static int send_name_query(int fd, const char *name, int query_ipv4, int query_ipv6) {
+static int send_name_query(int fd, const char *name, uint16_t id, int query_ipv4, int query_ipv6) {
     int ret = -1;
     struct dns_packet *p = NULL;
     uint8_t *prev_name = NULL;
@@ -297,6 +301,7 @@ static int send_name_query(int fd, const char *name, int query_ipv4, int query_i
         goto finish;
     }
 
+    dns_packet_set_field(p, DNS_FIELD_ID, id);
     dns_packet_set_field(p, DNS_FIELD_FLAGS, DNS_FLAGS(0, 0, 0, 0, 0, 0, 0, 0, 0, 0));
 
 #ifndef NSS_IP6_ONLY
@@ -354,7 +359,24 @@ static int domain_cmp(const char *a, const char *b) {
     return strncasecmp(a, b, al);
 }
 
-static int process_name_response(int fd, const char *name, usec_t timeout, void (*ipv4_func)(const ipv4_address_t *ipv4, void *userdata), void (*ipv6_func)(const ipv6_address_t *ipv6, void *userdata), void *userdata) {
+static int skip_questions(struct dns_packet *p) {
+    unsigned i;
+    assert(p);
+
+    for (i = dns_packet_get_field(p, DNS_FIELD_QDCOUNT); i > 0; i--) {
+        char pname[256];
+        uint16_t type, class;
+        
+        if (dns_packet_consume_name(p, pname, sizeof(pname)) < 0 ||
+            dns_packet_consume_uint16(p, &type) < 0 ||
+            dns_packet_consume_uint16(p, &class) < 0)
+            return -1;
+    }
+
+    return 0;
+}
+
+static int process_name_response(int fd, const char *name, usec_t timeout, uint16_t id, void (*ipv4_func)(const ipv4_address_t *ipv4, void *userdata), void (*ipv6_func)(const ipv6_address_t *ipv6, void *userdata), void *userdata) {
     struct dns_packet *p = NULL;
     int done = 0;
     struct timeval end;
@@ -374,12 +396,15 @@ static int process_name_response(int fd, const char *name, usec_t timeout, void
             return 1;
 
         /* Ignore packets with RFC != 255 */
-        if (ttl == 255) {
+        if (/* ttl == 255 && */  
+            dns_packet_check_valid_response(p) >= 0 &&
+            dns_packet_get_field(p, DNS_FIELD_ID) == id) {
+
+            unsigned i;
 
-            /* Ignore corrupt packets */
-            if (dns_packet_check_valid_response(p) >= 0) {
+            if (skip_questions(p) >= 0)
                 
-                for (;;) {
+                for (i = dns_packet_get_field(p, DNS_FIELD_ANCOUNT); i > 0; i--) {
                     char pname[256];
                     uint16_t type, class;
                     uint32_t rr_ttl;
@@ -392,7 +417,7 @@ static int process_name_response(int fd, const char *name, usec_t timeout, void
                         dns_packet_consume_uint16(p, &rdlength) < 0) {
                         break;
                     }
-
+                    
                     /* Remove mDNS cache flush bit */
                     class &= ~0x8000;
                     
@@ -402,27 +427,27 @@ static int process_name_response(int fd, const char *name, usec_t timeout, void
                         class == DNS_CLASS_IN &&
                         !domain_cmp(name, pname) &&
                         rdlength == sizeof(ipv4_address_t)) {
-
+                        
                         ipv4_address_t ipv4;
                         
                         if (dns_packet_consume_bytes(p, &ipv4, sizeof(ipv4)) < 0)
                             break;
-
+                        
                         ipv4_func(&ipv4, userdata);
                         done = 1;
                         
                     }
 #endif
 #if ! defined(NSS_IPV6_ONLY) && ! defined(NSS_IPV4_ONLY)
-                    else
+/*                     else  */
 #endif                        
 #ifndef NSS_IPV4_ONLY
-                        if (ipv6_func &&
-                               type == DNS_TYPE_AAAA &&
-                               class == DNS_CLASS_IN &&
-                               !domain_cmp(name, pname) &&
-                               rdlength == sizeof(ipv6_address_t)) {
-
+                    if (ipv6_func &&
+                        type == DNS_TYPE_AAAA &&
+                        class == DNS_CLASS_IN &&
+                        !domain_cmp(name, pname) &&
+                        rdlength == sizeof(ipv6_address_t)) {
+                        
                         ipv6_address_t ipv6;
                         
                         if (dns_packet_consume_bytes(p, &ipv6, sizeof(ipv6_address_t)) < 0)
@@ -432,35 +457,40 @@ static int process_name_response(int fd, const char *name, usec_t timeout, void
                         done = 1;
                     }
 #endif
-                        else {
-
+                    else {
+                        
                         /* Step over */
                         
                         if (dns_packet_consume_seek(p, rdlength) < 0)
                             break;
                     }
                 }
-            }
         }
 
+        
         if (p)
             dns_packet_free(p);
-    }
 
+    }
+    
     return 0;
 }
 
 int mdns_query_name(int fd, const char *name, void (*ipv4_func)(const ipv4_address_t *ipv4, void *userdata), void (*ipv6_func)(const ipv6_address_t *ipv6, void *userdata), void *userdata) {
     const usec_t *timeout = retry_ms;
+    uint16_t id;
+    
     assert(fd >= 0 && name && (ipv4_func || ipv6_func));
 
+    id = get_random_id();
+
     while (*timeout > 0) {
         int n;
         
-        if (send_name_query(fd, name, !!ipv4_func, !!ipv6_func) < 0)
+        if (send_name_query(fd, name, id, !!ipv4_func, !!ipv6_func) < 0)
             return -1;
 
-        if ((n = process_name_response(fd, name, *timeout, ipv4_func, ipv6_func, userdata)) < 0)
+        if ((n = process_name_response(fd, name, *timeout, id, ipv4_func, ipv6_func, userdata)) < 0)
             return -1;
 
         if (n == 0)
@@ -474,7 +504,7 @@ int mdns_query_name(int fd, const char *name, void (*ipv4_func)(const ipv4_addre
     return -1;
 }
 
-static int send_reverse_query(int fd, const char *name) {
+static int send_reverse_query(int fd, const char *name, uint16_t id) {
     int ret = -1;
     struct dns_packet *p = NULL;
 
@@ -485,6 +515,7 @@ static int send_reverse_query(int fd, const char *name) {
         goto finish;
     }
 
+    dns_packet_set_field(p, DNS_FIELD_ID, id);
     dns_packet_set_field(p, DNS_FIELD_FLAGS, DNS_FLAGS(0, 0, 0, 0, 0, 0, 0, 0, 0, 0));
 
     if (!dns_packet_append_name(p, name)) {
@@ -506,7 +537,7 @@ finish:
     return ret;
 }
 
-static int process_reverse_response(int fd, const char *name, usec_t timeout, void (*name_func)(const char *name, void *userdata), void *userdata) {
+static int process_reverse_response(int fd, const char *name, usec_t timeout, uint16_t id, void (*name_func)(const char *name, void *userdata), void *userdata) {
     struct dns_packet *p = NULL;
     int done = 0;
     struct timeval end;
@@ -526,12 +557,15 @@ static int process_reverse_response(int fd, const char *name, usec_t timeout, vo
             return 1;
 
         /* Ignore packets with RFC != 255 */
-        if (ttl == 255) {
+        if (/* ttl == 255 && */
+            dns_packet_check_valid_response(p) >= 0 &&
+            dns_packet_get_field(p, DNS_FIELD_ID) == id) {
 
-            /* Ignore corrupt packets */
-            if (dns_packet_check_valid_response(p) >= 0) {
-                
-                for (;;) {
+            unsigned i;
+
+            if (skip_questions(p) >= 0) {
+            
+                for (i = dns_packet_get_field(p, DNS_FIELD_ANCOUNT); i > 0; i--) {
                     char pname[256];
                     uint16_t type, class;
                     uint32_t rr_ttl;
@@ -544,24 +578,24 @@ static int process_reverse_response(int fd, const char *name, usec_t timeout, vo
                         dns_packet_consume_uint16(p, &rdlength) < 0) {
                         break;
                     }
-
+                    
                     /* Remove mDNS cache flush bit */
                     class &= ~0x8000;
                     
                     if (type == DNS_TYPE_PTR &&
                         class == DNS_CLASS_IN &&
                         !domain_cmp(name, pname)) {
-
+                        
                         char rname[256];
-
+                        
                         if (dns_packet_consume_name(p, rname, sizeof(rname)) < 0)
                             break;
-
+                        
                         name_func(rname, userdata);
                         done = 1;
                         
                     } else {
-
+                        
                         /* Step over */
                         
                         if (dns_packet_consume_seek(p, rdlength) < 0)
@@ -580,15 +614,19 @@ static int process_reverse_response(int fd, const char *name, usec_t timeout, vo
 
 static int query_reverse(int fd, const char *name, void (*name_func)(const char *name, void *userdata), void *userdata) {
     const usec_t *timeout = retry_ms;
+    uint16_t id;
+    
     assert(fd >= 0 && name && name_func);
 
+    id = get_random_id();
+    
     while (*timeout > 0) {
         int n;
         
-        if (send_reverse_query(fd, name) <= 0) /* error or no interface to send data on */
+        if (send_reverse_query(fd, name, id) <= 0) /* error or no interface to send data on */
             return -1;
 
-        if ((n = process_reverse_response(fd, name, *timeout, name_func, userdata)) < 0)
+        if ((n = process_reverse_response(fd, name, *timeout, id, name_func, userdata)) < 0)
             return -1;
 
         if (n == 0)
@@ -616,7 +654,7 @@ int mdns_query_ipv4(int fd, const ipv4_address_t *ipv4, void (*name_func)(const
 #endif
 
 #ifndef NSS_IPV4_ONLY
-static int mdns_query_ipv6(int fd, const ipv6_address_t *ipv6, void (*name_func)(const char *name, void *userdata), void *userdata) {
+int mdns_query_ipv6(int fd, const ipv6_address_t *ipv6, void (*name_func)(const char *name, void *userdata), void *userdata) {
     char name[256];
     assert(fd >= 0 && ipv6 && name_func);
 
-- 
cgit