On 3/6/18 3:02 PM, Lawrence Kreeger wrote:
> Hello,
>
> I'm trying to run mstpd on a per VLAN basis using one traditional
> linux bridge per VLAN. I'm running it on kernel version 4.12.4. It
> works fine for untagged frames, but I'm having a problem with VLAN
> tagged BPDUs arriving on the socket with the ifindex of the bridge
> itself, and not the VLAN tagged interface. For example, I have a
> tagged interface eth0.100 connected to the bridge "vlan100". When
> packets arrive, they have the ifindex of vlan100, which mstpd doesn't
> recognize as a valid spanning tree interface, so it drops them. Is
> there something needed to be set in the kernel to get the ifindex of
> eth0.100 instead? This is how mstpd opens the raw socket:
>
>
> /* Berkeley Packet filter code to filter out spanning tree packets.
> from tcpdump -s 1152 -dd stp
> */
> static struct sock_filter stp_filter[] = {
> { 0x28, 0, 0, 0x0000000c },
> { 0x25, 3, 0, 0x000005dc },
> { 0x30, 0, 0, 0x0000000e },
> { 0x15, 0, 1, 0x00000042 },
> { 0x6, 0, 0, 0x00000480 },
> { 0x6, 0, 0, 0x00000000 },
> };
>
> /*
> * Open up a raw packet socket to catch all 802.2 packets.
> * and install a packet filter to only see STP (SAP 42)
> *
> * Since any bridged devices are already in promiscious mode
> * no need to add multicast address.
> */
> int packet_sock_init(void)
> {
> int s;
> struct sock_fprog prog =
> {
> .len = sizeof(stp_filter) / sizeof(stp_filter[0]),
> .filter = stp_filter,
> };
>
> s = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_802_2));
try ETH_P_ALL
> if(s < 0)
> {
> ERROR("socket failed: %m");
> return -1;
> }
>
> if(setsockopt(s, SOL_SOCKET, SO_ATTACH_FILTER, &prog, sizeof(prog)) < 0)
> ERROR("setsockopt packet filter failed: %m");
> else if(fcntl(s, F_SETFL, O_NONBLOCK) < 0)
> ERROR("fcntl set nonblock failed: %m");
> else
> {
> packet_event.fd = s;
> packet_event.handler = packet_rcv;
And then packet_rcv using recvfrom:
struct sockaddr_ll sll;
char buf[4096];
socklen_t alen;
int len;
alen = sizeof(sll);
len = recvfrom(sd, buf, sizeof(buf), 0,
(struct sockaddr *)&sll, &alen);
And sll.sll_ifindex will show vlan device indices.
>
> if(0 == add_epoll(&packet_event))
> return 0;
> }
>
> close(s);
> return -1;
> }
>
> Thanks, Larry
>
