![Willem de Bruijn](/assets/img/avatar_default.png)
Tuntap and similar devices can inject GSO packets. Accept type VIRTIO_NET_HDR_GSO_UDP, even though not generating UFO natively. Processes are expected to use feature negotiation such as TUNSETOFFLOAD to detect supported offload types and refrain from injecting other packets. This process breaks down with live migration: guest kernels do not renegotiate flags, so destination hosts need to expose all features that the source host does. Partially revert the UFO removal from 182e0b6b5846~1..d9d30adf5677. This patch introduces nearly(*) no new code to simplify verification. It brings back verbatim tuntap UFO negotiation, VIRTIO_NET_HDR_GSO_UDP insertion and software UFO segmentation. It does not reinstate protocol stack support, hardware offload (NETIF_F_UFO), SKB_GSO_UDP tunneling in SKB_GSO_SOFTWARE or reception of VIRTIO_NET_HDR_GSO_UDP packets in tuntap. To support SKB_GSO_UDP reappearing in the stack, also reinstate logic in act_csum and openvswitch. Achieve equivalence with v4.13 HEAD by squashing in commit939912216f
("net: skb_needs_check() removes CHECKSUM_UNNECESSARY check for tx.") and reverting commit8d63bee643
("net: avoid skb_warn_bad_offload false positives on UFO"). (*) To avoid having to bring back skb_shinfo(skb)->ip6_frag_id, ipv6_proxy_select_ident is changed to return a __be32 and this is assigned directly to the frag_hdr. Also, SKB_GSO_UDP is inserted at the end of the enum to minimize code churn. Tested Booted a v4.13 guest kernel with QEMU. On a host kernel before this patch `ethtool -k eth0` shows UFO disabled. After the patch, it is enabled, same as on a v4.13 host kernel. A UFO packet sent from the guest appears on the tap device: host: nc -l -p -u 8000 & tcpdump -n -i tap0 guest: dd if=/dev/zero of=payload.txt bs=1 count=2000 nc -u 192.16.1.1 8000 < payload.txt Direct tap to tap transmission of VIRTIO_NET_HDR_GSO_UDP succeeds, packets arriving fragmented: ./with_tap_pair.sh ./tap_send_ufo tap0 tap1 (from https://github.com/wdebruij/kerneltools/tree/master/tests) Changes v1 -> v2 - simplified set_offload change (review comment) - documented test procedure Link: http://lkml.kernel.org/r/<CAF=yD-LuUeDuL9YWPJD9ykOZ0QCjNeznPDr6whqZ9NGMNF12Mw@mail.gmail.com> Fixes:fb652fdfe8
("macvlan/macvtap: Remove NETIF_F_UFO advertisement.") Reported-by: Michal Kubecek <mkubecek@suse.cz> Signed-off-by: Willem de Bruijn <willemb@google.com> Acked-by: Jason Wang <jasowang@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
172 lines
4.6 KiB
C
172 lines
4.6 KiB
C
/*
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* IPV6 GSO/GRO offload support
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* Linux INET6 implementation
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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* UDPv6 GSO support
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*/
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#include <linux/skbuff.h>
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#include <linux/netdevice.h>
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#include <net/protocol.h>
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#include <net/ipv6.h>
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#include <net/udp.h>
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#include <net/ip6_checksum.h>
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#include "ip6_offload.h"
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static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb,
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netdev_features_t features)
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{
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struct sk_buff *segs = ERR_PTR(-EINVAL);
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unsigned int mss;
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unsigned int unfrag_ip6hlen, unfrag_len;
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struct frag_hdr *fptr;
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u8 *packet_start, *prevhdr;
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u8 nexthdr;
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u8 frag_hdr_sz = sizeof(struct frag_hdr);
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__wsum csum;
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int tnl_hlen;
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int err;
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mss = skb_shinfo(skb)->gso_size;
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if (unlikely(skb->len <= mss))
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goto out;
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if (skb->encapsulation && skb_shinfo(skb)->gso_type &
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(SKB_GSO_UDP_TUNNEL|SKB_GSO_UDP_TUNNEL_CSUM))
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segs = skb_udp_tunnel_segment(skb, features, true);
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else {
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const struct ipv6hdr *ipv6h;
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struct udphdr *uh;
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if (!pskb_may_pull(skb, sizeof(struct udphdr)))
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goto out;
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/* Do software UFO. Complete and fill in the UDP checksum as HW cannot
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* do checksum of UDP packets sent as multiple IP fragments.
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*/
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uh = udp_hdr(skb);
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ipv6h = ipv6_hdr(skb);
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uh->check = 0;
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csum = skb_checksum(skb, 0, skb->len, 0);
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uh->check = udp_v6_check(skb->len, &ipv6h->saddr,
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&ipv6h->daddr, csum);
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if (uh->check == 0)
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uh->check = CSUM_MANGLED_0;
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skb->ip_summed = CHECKSUM_UNNECESSARY;
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/* If there is no outer header we can fake a checksum offload
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* due to the fact that we have already done the checksum in
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* software prior to segmenting the frame.
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*/
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if (!skb->encap_hdr_csum)
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features |= NETIF_F_HW_CSUM;
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/* Check if there is enough headroom to insert fragment header. */
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tnl_hlen = skb_tnl_header_len(skb);
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if (skb->mac_header < (tnl_hlen + frag_hdr_sz)) {
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if (gso_pskb_expand_head(skb, tnl_hlen + frag_hdr_sz))
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goto out;
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}
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/* Find the unfragmentable header and shift it left by frag_hdr_sz
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* bytes to insert fragment header.
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*/
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err = ip6_find_1stfragopt(skb, &prevhdr);
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if (err < 0)
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return ERR_PTR(err);
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unfrag_ip6hlen = err;
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nexthdr = *prevhdr;
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*prevhdr = NEXTHDR_FRAGMENT;
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unfrag_len = (skb_network_header(skb) - skb_mac_header(skb)) +
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unfrag_ip6hlen + tnl_hlen;
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packet_start = (u8 *) skb->head + SKB_GSO_CB(skb)->mac_offset;
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memmove(packet_start-frag_hdr_sz, packet_start, unfrag_len);
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SKB_GSO_CB(skb)->mac_offset -= frag_hdr_sz;
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skb->mac_header -= frag_hdr_sz;
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skb->network_header -= frag_hdr_sz;
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fptr = (struct frag_hdr *)(skb_network_header(skb) + unfrag_ip6hlen);
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fptr->nexthdr = nexthdr;
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fptr->reserved = 0;
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fptr->identification = ipv6_proxy_select_ident(dev_net(skb->dev), skb);
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/* Fragment the skb. ipv6 header and the remaining fields of the
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* fragment header are updated in ipv6_gso_segment()
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*/
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segs = skb_segment(skb, features);
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}
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out:
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return segs;
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}
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static struct sk_buff **udp6_gro_receive(struct sk_buff **head,
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struct sk_buff *skb)
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{
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struct udphdr *uh = udp_gro_udphdr(skb);
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if (unlikely(!uh))
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goto flush;
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/* Don't bother verifying checksum if we're going to flush anyway. */
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if (NAPI_GRO_CB(skb)->flush)
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goto skip;
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if (skb_gro_checksum_validate_zero_check(skb, IPPROTO_UDP, uh->check,
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ip6_gro_compute_pseudo))
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goto flush;
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else if (uh->check)
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skb_gro_checksum_try_convert(skb, IPPROTO_UDP, uh->check,
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ip6_gro_compute_pseudo);
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skip:
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NAPI_GRO_CB(skb)->is_ipv6 = 1;
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return udp_gro_receive(head, skb, uh, udp6_lib_lookup_skb);
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flush:
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NAPI_GRO_CB(skb)->flush = 1;
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return NULL;
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}
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static int udp6_gro_complete(struct sk_buff *skb, int nhoff)
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{
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const struct ipv6hdr *ipv6h = ipv6_hdr(skb);
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struct udphdr *uh = (struct udphdr *)(skb->data + nhoff);
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if (uh->check) {
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skb_shinfo(skb)->gso_type |= SKB_GSO_UDP_TUNNEL_CSUM;
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uh->check = ~udp_v6_check(skb->len - nhoff, &ipv6h->saddr,
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&ipv6h->daddr, 0);
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} else {
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skb_shinfo(skb)->gso_type |= SKB_GSO_UDP_TUNNEL;
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}
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return udp_gro_complete(skb, nhoff, udp6_lib_lookup_skb);
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}
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static const struct net_offload udpv6_offload = {
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.callbacks = {
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.gso_segment = udp6_ufo_fragment,
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.gro_receive = udp6_gro_receive,
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.gro_complete = udp6_gro_complete,
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},
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};
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int udpv6_offload_init(void)
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{
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return inet6_add_offload(&udpv6_offload, IPPROTO_UDP);
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}
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int udpv6_offload_exit(void)
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{
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return inet6_del_offload(&udpv6_offload, IPPROTO_UDP);
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}
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