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Packet Filter Linux ignore VLAN tagged packets #119

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Packet Filter Linux ignore VLAN tagged packets #119

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44 changes: 42 additions & 2 deletions src/lib/dhcp/pkt_filter_lpf.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -180,6 +180,15 @@ PktFilterLPF::openSocket(Iface& iface,
<< " on the socket " << sock);
}

int one = 1;
if(setsockopt(sock, SOL_PACKET, PACKET_AUXDATA, &one, sizeof(one)) < 0)
{
close(sock);
close(fallback);
isc_throw(SocketConfigError, "Failed to install packet aux data"
<< " on the socket " << sock);
}

struct sockaddr_ll sa;
memset(&sa, 0, sizeof(sockaddr_ll));
sa.sll_family = AF_PACKET;
Expand Down Expand Up @@ -216,6 +225,20 @@ PktFilterLPF::openSocket(Iface& iface,
Pkt4Ptr
PktFilterLPF::receive(Iface& iface, const SocketInfo& socket_info) {
uint8_t raw_buf[IfaceMgr::RCVBUFSIZE];
unsigned char cmsgbuf[CMSG_LEN(sizeof(struct tpacket_auxdata))];
struct iovec iov;
struct msghdr msg;
struct cmsghdr *cmsg;
uint16_t tp_vlan_tpid;

iov.iov_base = &raw_buf;
iov.iov_len = sizeof(raw_buf);

memset(&msg, 0, sizeof(msg));
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
msg.msg_control = cmsgbuf;
msg.msg_controllen = sizeof(cmsgbuf);
// First let's get some data from the fallback socket. The data will be
// discarded but we don't want the socket buffer to bloat. We get the
// packets from the socket in loop but most of the time the loop will
Expand All @@ -237,8 +260,11 @@ PktFilterLPF::receive(Iface& iface, const SocketInfo& socket_info) {

// Now that we finished getting data from the fallback socket, we
// have to get the data from the raw socket too.
int data_len = read(socket_info.sockfd_, raw_buf, sizeof(raw_buf));
// If negative value is returned by read(), it indicates that an
int data_len;
do {
data_len = recvmsg(socket_info.sockfd_, &msg, 0);
} while (data_len < 0 && errno == EINTR);
// If negative value is returned by recvmsg(), it indicates that an
// error occurred. If returned value is 0, no data was read from the
// socket. In both cases something has gone wrong, because we expect
// that a chunk of data is there. We signal the lack of data by
Expand All @@ -247,6 +273,20 @@ PktFilterLPF::receive(Iface& iface, const SocketInfo& socket_info) {
return Pkt4Ptr();
}

tp_vlan_tpid = 0;
for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
if (cmsg->cmsg_level == SOL_PACKET &&
cmsg->cmsg_type == PACKET_AUXDATA) {
struct tpacket_auxdata *aux = (struct tpacket_auxdata *)CMSG_DATA(cmsg);
tp_vlan_tpid = aux->tp_vlan_tpid;
}
}

// Only server non VLAN/QinQ Traffic
if (tp_vlan_tpid != 0) {
return Pkt4Ptr();
}

InputBuffer buf(raw_buf, data_len);

// @todo: This is awkward way to solve the chicken and egg problem
Expand Down