• Ananda Raju's avatar
    [IPv4/IPv6]: UFO Scatter-gather approach · e89e9cf5
    Ananda Raju authored
    
    
    Attached is kernel patch for UDP Fragmentation Offload (UFO) feature.
    
    1. This patch incorporate the review comments by Jeff Garzik.
    2. Renamed USO as UFO (UDP Fragmentation Offload)
    3. udp sendfile support with UFO
    
    This patches uses scatter-gather feature of skb to generate large UDP
    datagram. Below is a "how-to" on changes required in network device
    driver to use the UFO interface.
    
    UDP Fragmentation Offload (UFO) Interface:
    -------------------------------------------
    UFO is a feature wherein the Linux kernel network stack will offload the
    IP fragmentation functionality of large UDP datagram to hardware. This
    will reduce the overhead of stack in fragmenting the large UDP datagram to
    MTU sized packets
    
    1) Drivers indicate their capability of UFO using
    dev->features |= NETIF_F_UFO | NETIF_F_HW_CSUM | NETIF_F_SG
    
    NETIF_F_HW_CSUM is required for UFO over ipv6.
    
    2) UFO packet will be submitted for transmission using driver xmit routine.
    UFO packet will have a non-zero value for
    
    "skb_shinfo(skb)->ufo_size"
    
    skb_shinfo(skb)->ufo_size will indicate the length of data part in each IP
    fragment going out of the adapter after IP fragmentation by hardware.
    
    skb->data will contain MAC/IP/UDP header and skb_shinfo(skb)->frags[]
    contains the data payload. The skb->ip_summed will be set to CHECKSUM_HW
    indicating that hardware has to do checksum calculation. Hardware should
    compute the UDP checksum of complete datagram and also ip header checksum of
    each fragmented IP packet.
    
    For IPV6 the UFO provides the fragment identification-id in
    skb_shinfo(skb)->ip6_frag_id. The adapter should use this ID for generating
    IPv6 fragments.
    Signed-off-by: default avatarAnanda Raju <ananda.raju@neterion.com>
    Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (forwarded)
    Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@mandriva.com>
    e89e9cf5
skbuff.c 44.6 KB