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eh = *(mtod(m, struct ether_header *));
eh.ether_type = ntohs((unsigned short)eh.ether_type);
m->m_data += sizeof(struct ether_header);
ADD_RECV_PACKET(ifp, sc, m->m_pkthdr.len);
if (eh.ether_dhost[0] & 0x1) {
}
}
}
Calls the io_blockread( ) routine to perform the data transfer from
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the FIFO buffer on the adapter to the mbuf in host memory.
Makes a copy of the ether_header data structure for the
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ether_input( ) routine.
Converts the 2-byte ether_type field from network byte order to host
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byte order and saves it in the ether_header data structure.
Adjusts the pointer to the received data to point past the MAC header
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(skips past the destination address, source address, and ether_type
fields).
Calls the ADD_RECV_PACKET macro to increment the receive packet
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(block) count. If this packet was destined for a broadcast or multicast
address, calls the ADD_RECV_MPACKET macro to increment those
statistics as well.
Calls the READ_RXS macro to read the receive status. If the packet just
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received was not fully received, scraps the packet.
Calls the ether_input( ) routine to process the received Ethernet
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packet. The packet is in the mbuf chain without the ether_header
data structure, which is provided separately.
13.2.5 Discarding a Packet
The following code shows how the el_rint( ) routine discards a packet.
Some receive interrupt handlers perform a copy of a few bytes of the
packet to determine if the packet is actually destined for the device. Thus,
this task is an optional optimization.
scrap:
WRITE_CMD(sc, CMD_RXDTP);
status = READ_RXS(sc);
}
ADD_RECV_MPACKET(ifp, sc, m->m_pkthdr.len);
i = READ_RXS(sc);
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if (i &= 0x7ff) {
if ((i & 0x400) == 0) {
m_freem(m);
goto scrap;
}
}
ether_input(ifp, &eh, m);
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Implementing the Interrupt Section 13–9
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