packet: Add GSO/csum offload support.

This patch adds GSO/checksum offload to af_packet sockets using
virtio_net_hdr. Based on Rusty's patch to add this support to tun.
It allows GSO/checksum offload to be enabled when using raw socket
backend with virtio_net.
Adds PACKET_VNET_HDR socket option to prepend virtio_net_hdr in the
receive path and process/skip virtio_net_hdr in the send path. This
option is only allowed with SOCK_RAW sockets attached to ethernet
type devices.

v2 updates
----------
Michael's Comments
- Perform length check in packet_snd() when GSO is off even when
  vnet_hdr is present.
- Check for SKB_GSO_FCOE type and return -EINVAL
- don't allow tx/rx ring when vnet_hdr is enabled.
Herbert's Comments
- Removed ethernet specific code.
- protocol value is assumed to be passed in by the caller.

Signed-off-by: Sridhar Samudrala <sri@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 177 insertions, 11 deletions

diff --git a/include/linux/if_packet.h b/include/linux/if_packet.h
index 4021d47cc437..aa57a5f993fc 100644
--- a/include/linux/if_packet.h
+++ b/include/linux/if_packet.h
@@ -46,6 +46,7 @@ struct sockaddr_ll {
 #define PACKET_RESERVE                  12
 #define PACKET_TX_RING                  13
 #define PACKET_LOSS                     14
+#define PACKET_VNET_HDR                 15
 
 struct tpacket_stats {
         unsigned int    tp_packets;
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 53633c5fdb1d..178e2937bbaa 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -80,6 +80,7 @@
 #include <linux/init.h>
 #include <linux/mutex.h>
 #include <linux/if_vlan.h>
+#include <linux/virtio_net.h>
 
 #ifdef CONFIG_INET
 #include <net/inet_common.h>
@@ -193,7 +194,8 @@ struct packet_sock {
         struct mutex            pg_vec_lock;
         unsigned int            running:1,      /* prot_hook is attached*/
                                 auxdata:1,
-                                origdev:1;
+                                origdev:1,
+                                has_vnet_hdr:1;
         int                     ifindex;        /* bound device         */
         __be16                  num;
         struct packet_mclist    *mclist;
@@ -1056,6 +1058,30 @@ out:
 }
 #endif
 
+static inline struct sk_buff *packet_alloc_skb(struct sock *sk, size_t prepad,
+                                               size_t reserve, size_t len,
+                                               size_t linear, int noblock,
+                                               int *err)
+{
+        struct sk_buff *skb;
+
+        /* Under a page?  Don't bother with paged skb. */
+        if (prepad + len < PAGE_SIZE || !linear)
+                linear = len;
+
+        skb = sock_alloc_send_pskb(sk, prepad + linear, len - linear, noblock,
+                                   err);
+        if (!skb)
+                return NULL;
+
+        skb_reserve(skb, reserve);
+        skb_put(skb, linear);
+        skb->data_len = len - linear;
+        skb->len += len - linear;
+
+        return skb;
+}
+
 static int packet_snd(struct socket *sock,
                           struct msghdr *msg, size_t len)
 {
@@ -1066,14 +1092,17 @@ static int packet_snd(struct socket *sock,
         __be16 proto;
         unsigned char *addr;
         int ifindex, err, reserve = 0;
+        struct virtio_net_hdr vnet_hdr = { 0 };
+        int offset = 0;
+        int vnet_hdr_len;
+        struct packet_sock *po = pkt_sk(sk);
+        unsigned short gso_type = 0;
 
         /*
          *      Get and verify the address.
          */
 
         if (saddr == NULL) {
-                struct packet_sock *po = pkt_sk(sk);
-
                 ifindex = po->ifindex;
                 proto   = po->num;
                 addr    = NULL;
@@ -1100,25 +1129,74 @@ static int packet_snd(struct socket *sock,
         if (!(dev->flags & IFF_UP))
                 goto out_unlock;
 
+        if (po->has_vnet_hdr) {
+                vnet_hdr_len = sizeof(vnet_hdr);
+
+                err = -EINVAL;
+                if (len < vnet_hdr_len)
+                        goto out_unlock;
+
+                len -= vnet_hdr_len;
+
+                err = memcpy_fromiovec((void *)&vnet_hdr, msg->msg_iov,
+                                       vnet_hdr_len);
+                if (err < 0)
+                        goto out_unlock;
+
+                if ((vnet_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
+                    (vnet_hdr.csum_start + vnet_hdr.csum_offset + 2 >
+                      vnet_hdr.hdr_len))
+                        vnet_hdr.hdr_len = vnet_hdr.csum_start +
+                                                 vnet_hdr.csum_offset + 2;
+
+                err = -EINVAL;
+                if (vnet_hdr.hdr_len > len)
+                        goto out_unlock;
+
+                if (vnet_hdr.gso_type != VIRTIO_NET_HDR_GSO_NONE) {
+                        switch (vnet_hdr.gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {
+                        case VIRTIO_NET_HDR_GSO_TCPV4:
+                                gso_type = SKB_GSO_TCPV4;
+                                break;
+                        case VIRTIO_NET_HDR_GSO_TCPV6:
+                                gso_type = SKB_GSO_TCPV6;
+                                break;
+                        case VIRTIO_NET_HDR_GSO_UDP:
+                                gso_type = SKB_GSO_UDP;
+                                break;
+                        default:
+                                goto out_unlock;
+                        }
+
+                        if (vnet_hdr.gso_type & VIRTIO_NET_HDR_GSO_ECN)
+                                gso_type |= SKB_GSO_TCP_ECN;
+
+                        if (vnet_hdr.gso_size == 0)
+                                goto out_unlock;
+
+                }
+        }
+
         err = -EMSGSIZE;
-        if (len > dev->mtu+reserve)
+        if (!gso_type && (len > dev->mtu+reserve))
                 goto out_unlock;
 
-        skb = sock_alloc_send_skb(sk, len + LL_ALLOCATED_SPACE(dev),
-                                msg->msg_flags & MSG_DONTWAIT, &err);
+        err = -ENOBUFS;
+        skb = packet_alloc_skb(sk, LL_ALLOCATED_SPACE(dev),
+                               LL_RESERVED_SPACE(dev), len, vnet_hdr.hdr_len,
+                               msg->msg_flags & MSG_DONTWAIT, &err);
         if (skb == NULL)
                 goto out_unlock;
 
-        skb_reserve(skb, LL_RESERVED_SPACE(dev));
-        skb_reset_network_header(skb);
+        skb_set_network_header(skb, reserve);
 
         err = -EINVAL;
         if (sock->type == SOCK_DGRAM &&
-            dev_hard_header(skb, dev, ntohs(proto), addr, NULL, len) < 0)
+            (offset = dev_hard_header(skb, dev, ntohs(proto), addr, NULL, len)) < 0)
                 goto out_free;
 
         /* Returns -EFAULT on error */
-        err = memcpy_fromiovec(skb_put(skb, len), msg->msg_iov, len);
+        err = skb_copy_datagram_from_iovec(skb, offset, msg->msg_iov, 0, len);
         if (err)
                 goto out_free;
 
@@ -1127,6 +1205,25 @@ static int packet_snd(struct socket *sock,
         skb->priority = sk->sk_priority;
         skb->mark = sk->sk_mark;
 
+        if (po->has_vnet_hdr) {
+                if (vnet_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
+                        if (!skb_partial_csum_set(skb, vnet_hdr.csum_start,
+                                                  vnet_hdr.csum_offset)) {
+                                err = -EINVAL;
+                                goto out_free;
+                        }
+                }
+
+                skb_shinfo(skb)->gso_size = vnet_hdr.gso_size;
+                skb_shinfo(skb)->gso_type = gso_type;
+
+                /* Header must be checked, and gso_segs computed. */
+                skb_shinfo(skb)->gso_type |= SKB_GSO_DODGY;
+                skb_shinfo(skb)->gso_segs = 0;
+
+                len += vnet_hdr_len;
+        }
+
         /*
          *      Now send it
          */
@@ -1420,6 +1517,7 @@ static int packet_recvmsg(struct kiocb *iocb, struct socket *sock,
         struct sk_buff *skb;
         int copied, err;
         struct sockaddr_ll *sll;
+        int vnet_hdr_len = 0;
 
         err = -EINVAL;
         if (flags & ~(MSG_PEEK|MSG_DONTWAIT|MSG_TRUNC|MSG_CMSG_COMPAT))
@@ -1451,6 +1549,48 @@ static int packet_recvmsg(struct kiocb *iocb, struct socket *sock,
         if (skb == NULL)
                 goto out;
 
+        if (pkt_sk(sk)->has_vnet_hdr) {
+                struct virtio_net_hdr vnet_hdr = { 0 };
+
+                err = -EINVAL;
+                vnet_hdr_len = sizeof(vnet_hdr);
+                if ((len -= vnet_hdr_len) < 0)
+                        goto out_free;
+
+                if (skb_is_gso(skb)) {
+                        struct skb_shared_info *sinfo = skb_shinfo(skb);
+
+                        /* This is a hint as to how much should be linear. */
+                        vnet_hdr.hdr_len = skb_headlen(skb);
+                        vnet_hdr.gso_size = sinfo->gso_size;
+                        if (sinfo->gso_type & SKB_GSO_TCPV4)
+                                vnet_hdr.gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
+                        else if (sinfo->gso_type & SKB_GSO_TCPV6)
+                                vnet_hdr.gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
+                        else if (sinfo->gso_type & SKB_GSO_UDP)
+                                vnet_hdr.gso_type = VIRTIO_NET_HDR_GSO_UDP;
+                        else if (sinfo->gso_type & SKB_GSO_FCOE)
+                                goto out_free;
+                        else
+                                BUG();
+                        if (sinfo->gso_type & SKB_GSO_TCP_ECN)
+                                vnet_hdr.gso_type |= VIRTIO_NET_HDR_GSO_ECN;
+                } else
+                        vnet_hdr.gso_type = VIRTIO_NET_HDR_GSO_NONE;
+
+                if (skb->ip_summed == CHECKSUM_PARTIAL) {
+                        vnet_hdr.flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
+                        vnet_hdr.csum_start = skb->csum_start -
+                                                        skb_headroom(skb);
+                        vnet_hdr.csum_offset = skb->csum_offset;
+                } /* else everything is zero */
+
+                err = memcpy_toiovec(msg->msg_iov, (void *)&vnet_hdr,
+                                     vnet_hdr_len);
+                if (err < 0)
+                        goto out_free;
+        }
+
         /*
          *      If the address length field is there to be filled in, we fill
          *      it in now.
@@ -1502,7 +1642,7 @@ static int packet_recvmsg(struct kiocb *iocb, struct socket *sock,
          *      Free or return the buffer as appropriate. Again this
          *      hides all the races and re-entrancy issues from us.
          */
-        err = (flags&MSG_TRUNC) ? skb->len : copied;
+        err = vnet_hdr_len + ((flags&MSG_TRUNC) ? skb->len : copied);
 
 out_free:
         skb_free_datagram(sk, skb);
@@ -1740,6 +1880,8 @@ packet_setsockopt(struct socket *sock, int level, int optname, char __user *optv
 
                 if (optlen < sizeof(req))
                         return -EINVAL;
+                if (pkt_sk(sk)->has_vnet_hdr)
+                        return -EINVAL;
                 if (copy_from_user(&req, optval, sizeof(req)))
                         return -EFAULT;
                 return packet_set_ring(sk, &req, 0, optname == PACKET_TX_RING);
@@ -1826,6 +1968,22 @@ packet_setsockopt(struct socket *sock, int level, int optname, char __user *optv
                 po->origdev = !!val;
                 return 0;
         }
+        case PACKET_VNET_HDR:
+        {
+                int val;
+
+                if (sock->type != SOCK_RAW)
+                        return -EINVAL;
+                if (po->rx_ring.pg_vec || po->tx_ring.pg_vec)
+                        return -EBUSY;
+                if (optlen < sizeof(val))
+                        return -EINVAL;
+                if (copy_from_user(&val, optval, sizeof(val)))
+                        return -EFAULT;
+
+                po->has_vnet_hdr = !!val;
+                return 0;
+        }
         default:
                 return -ENOPROTOOPT;
         }
@@ -1876,6 +2034,13 @@ static int packet_getsockopt(struct socket *sock, int level, int optname,
 
                 data = &val;
                 break;
+        case PACKET_VNET_HDR:
+                if (len > sizeof(int))
+                        len = sizeof(int);
+                val = po->has_vnet_hdr;
+
+                data = &val;
+                break;
 #ifdef CONFIG_PACKET_MMAP
         case PACKET_VERSION:
                 if (len > sizeof(int))