Hi all!
I'm trying to receive multicast packets sent using a tunnel.
int main()
{ int fd;
struct ip_mreqn mreq;
mreq.imr_multiaddr.s_addr = inet_addr("224.0.0.5");
mreq.imr_address.s_addr = inet_addr("x.x.x.x");
mreq.imr_ifindex = 8;
int maxpktlen = 1500;
if ((fd = socket(AF_INET,SOCK_RAW,OSPF_PROTOCOL)) == -1)
panic("pkt::socket: socket error");
setsockopt(fd,IPPROTO_IP,IP_ADD_MEMBERSHIP,&mreq,sizeof(mreq));
unsigned char* buf = new unsigned char[maxpktlen];
if (!buf)
panic("pkt::receive: memory allocation error");
n = recv(fd,buf,maxpktlen,0);
}
When mreq.imr_ifindex = 7 (eth2), everything works fine.
With mreq.imr_ifindex = 8 (gre1), recv never returns.
netstat says the nic is configured to recv these mcasts:
gondolin:~# netstat -g -n
IPv4 Group Memberships
Interface RefCnt Group
--------------- ------ ---------------------
lo 1 224.0.0.1
eth0 1 224.0.1.1
eth0 1 224.0.0.1
eth1 1 224.0.0.1
eth2 1 224.0.0.1
gre1 1 224.0.0.5
gre1 1 224.0.0.1
gre2 1 224.0.0.1
tcpdump says it's receiving mcasts to 224.0.0.5:
gondolin:~# tcpdump -i gre1 -n
Kernel filter, protocol ALL, datagram packet socket
tcpdump: listening on gre1
12:11:27.211136 < x.x.x.x > 224.0.0.5: OSPFv2-hello 44: rtrid x.x.x.x
backbone [tos 0xc0] [ttl 1]
I'm using kernel 2.2.13.
Does anyone know what i'm doing wrong?
Thank you for your help,
Eric.
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