From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Athan Subject: Cannot receive multicast packets Date: Thu, 20 Apr 2006 15:24:13 -0400 Message-ID: <4447DFDD.8010008@cloakmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail.thinktradellc.com ([66.54.171.98]:21764 "EHLO mail.thinktradellc.com") by vger.kernel.org with ESMTP id S1750927AbWDTTYO (ORCPT ); Thu, 20 Apr 2006 15:24:14 -0400 To: netdev@vger.kernel.org Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org I sent a similar message to LKML, and linux-dev but was directed to this list might as most appropriate. Thanks in advance... It's likely this is a programming error, but I am at a loss. The simple UDP multicast receive application below, adapted from source on IBM's web site, will not receive any data. While it is blocked on recv(): hfclinux2:/home/root/UDP/apps/Crosser2# netstat -ang IPv6/IPv4 Group Memberships Interface RefCnt Group --------------- ------ --------------------- lo 1 224.0.0.1 eth0 1 224.0.0.1 eth1 1 224.0.17.44 eth1 1 224.0.0.1 lo 1 ff02::1 eth0 1 ff02::1:ffdd:eb2b eth0 1 ff02::1 eth1 1 ff02::1:ffdd:eb2c eth1 1 ff02::1 And tcpdump shows traffic arriving at the interface(see below)! This leads me to belive the kernel is filtering it, and or not delivering it to the socket. The one "strange" thing about this network is that the traffic is flowing in "dense mode", meaning there is no explicit need for IGMP messaging (nor any response to such messaging). Can anyone point me in the right direction regarding why the socket never receives any data???? Thanks. Andrew hfclinux2:/home/root/UDP/apps/Crosser2# uname -a Linux hfclinux2 2.6.15.1smp #6 SMP PREEMPT Mon Feb 13 11:38:32 EST 2006 i686 GNU/Linux hfclinux2:/home/root/UDP/apps/Crosser2# tcpdump -i eth1 port 55300 tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on eth1, link-type EN10MB (Ethernet), capture size 96 bytes 12:54:06.980000 IP 206.200.5.144.2232 > 224.0.17.44.55300: UDP, length 91 12:54:07.079675 IP 206.200.5.144.2232 > 224.0.17.44.55300: UDP, length 46 12:54:07.179869 IP 206.200.5.144.2232 > 224.0.17.44.55300: UDP, length 181 12:54:07.280437 IP 206.200.5.144.2232 > 224.0.17.44.55300: UDP, length 181 12:54:07.380005 IP 206.200.5.144.2232 > 224.0.17.44.55300: UDP, length 181 12:54:07.480073 IP 206.200.5.144.2232 > 224.0.17.44.55300: UDP, length 136 12:54:07.680459 IP 206.200.5.144.2232 > 224.0.17.44.55300: UDP, length 91 12:54:07.780277 IP 206.200.5.144.2232 > 224.0.17.44.55300: UDP, length 136 hfclinux2:/home/root/UDP/apps/Crosser2# ifconfig eth0 Link encap:Ethernet HWaddr 00:11:43:DD:EB:2B inet addr:172.22.71.128 Bcast:172.22.71.255 Mask:255.255.255.0 inet6 addr: fe80::211:43ff:fedd:eb2b/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:19540 errors:0 dropped:0 overruns:0 frame:0 TX packets:7838 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:1563190 (1.4 MiB) TX bytes:1943895 (1.8 MiB) Base address:0xdcc0 Memory:dfae0000-dfb00000 eth0:1 Link encap:Ethernet HWaddr 00:11:43:DD:EB:2B inet addr:10.61.6.128 Bcast:10.61.6.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 Base address:0xdcc0 Memory:dfae0000-dfb00000 eth0:2 Link encap:Ethernet HWaddr 00:11:43:DD:EB:2B inet addr:196.0.34.11 Bcast:196.0.34.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 Base address:0xdcc0 Memory:dfae0000-dfb00000 eth0:3 Link encap:Ethernet HWaddr 00:11:43:DD:EB:2B inet addr:192.168.254.128 Bcast:192.168.254.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 Base address:0xdcc0 Memory:dfae0000-dfb00000 eth1 Link encap:Ethernet HWaddr 00:11:43:DD:EB:2C inet addr:192.168.250.128 Bcast:192.168.250.255 Mask:255.255.255.0 inet6 addr: fe80::211:43ff:fedd:eb2c/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:137717 errors:0 dropped:0 overruns:0 frame:0 TX packets:24 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:58314262 (55.6 MiB) TX bytes:1596 (1.5 KiB) Base address:0xccc0 Memory:df8e0000-df900000 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:0 (0.0 b) TX bytes:0 (0.0 b) ------------------------- #include #include #include #include #include #include #include #include using namespace std; struct sockaddr_in localSock; struct ip_mreqn group; int sd; int datalen; char databuf[10]; int main (int argc, char *argv[]) { sd = socket(AF_INET, SOCK_DGRAM, 0); if (sd < 0) { perror("opening datagram socket"); exit(1); } { int reuse=1; if (setsockopt(sd, SOL_SOCKET, SO_REUSEADDR, (char *)&reuse, sizeof(reuse)) < 0) { perror("setting SO_REUSEADDR"); close(sd); exit(1); } } memset((char *) &localSock, 0, sizeof(localSock)); localSock.sin_family = AF_INET; localSock.sin_port = htons(55300);; localSock.sin_addr.s_addr = INADDR_ANY; if (bind(sd, (struct sockaddr*)&localSock, sizeof(localSock))) { perror("binding datagram socket"); close(sd); exit(1); } group.imr_multiaddr.s_addr = inet_addr("224.0.17.44"); printf("%d\n",group.imr_multiaddr.s_addr); group.imr_address.s_addr = inet_addr("192.168.250.128"); if (setsockopt(sd, IPPROTO_IP, IP_ADD_MEMBERSHIP, (char *)&group, sizeof(group)) < 0) { perror("adding multicast group"); close(sd); exit(1); } /* * Read from the socket. */ datalen = sizeof(databuf); if (recv(sd, databuf, datalen,0) < 0) { perror("reading datagram message"); close(sd); exit(1); } else { puts("success reading"); } }