[RFC PATCH 6/7] tun: populate hash in virtio-net header when needed

[Yuri Benditovich]

If the BPF program populated the hash in the skb the tun
propagates the hash value and hash report type to the
respective fields of virtio-net header.

Signed-off-by: Yuri Benditovich <yuri.benditov...@daynix.com>
---
 drivers/net/tun.c | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 45f4f04a4a3e..214feb0b16fb 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -556,15 +556,20 @@ static u16 tun_ebpf_select_queue(struct tun_struct *tun, 
struct sk_buff *skb)
 {
        struct tun_prog *prog;
        u32 numqueues;
-       u16 ret = 0;
+       u32 ret = 0;
 
        numqueues = READ_ONCE(tun->numqueues);
        if (!numqueues)
                return 0;
 
        prog = rcu_dereference(tun->steering_prog);
-       if (prog)
+       if (prog) {
                ret = bpf_prog_run_clear_cb(prog->prog, skb);
+               if (tun->bpf_populates_hash) {
+                       *skb_hash_report_type(skb) = (__u8)(ret >> 16);
+                       ret &= 0xffff;
+               }
+       }
 
        return ret % numqueues;
 }
@@ -2062,6 +2067,7 @@ static ssize_t tun_put_user(struct tun_struct *tun,
 
        if (vnet_hdr_sz) {
                struct virtio_net_hdr gso;
+               __u16 extra_copy = 0;
 
                if (iov_iter_count(iter) < vnet_hdr_sz)
                        return -EINVAL;
@@ -2085,7 +2091,20 @@ static ssize_t tun_put_user(struct tun_struct *tun,
                if (copy_to_iter(&gso, sizeof(gso), iter) != sizeof(gso))
                        return -EFAULT;
 
-               iov_iter_advance(iter, vnet_hdr_sz - sizeof(gso));
+               if (tun->bpf_populates_hash &&
+                   vnet_hdr_sz >= sizeof(struct virtio_net_hdr_v1_hash)) {
+                       struct virtio_net_hdr_v1_hash hdr;
+
+                       hdr.hdr.num_buffers = 0;
+                       hdr.hash_value = cpu_to_le32(skb_get_hash(skb));
+                       hdr.hash_report = 
cpu_to_le16(*skb_hash_report_type(skb));
+                       hdr.padding = 0;
+                       extra_copy = sizeof(hdr) - sizeof(gso);
+                       if (copy_to_iter(&hdr.hdr.num_buffers, extra_copy, 
iter) != extra_copy)
+                               return -EFAULT;
+               }
+
+               iov_iter_advance(iter, vnet_hdr_sz - sizeof(gso) - extra_copy);
        }
 
        if (vlan_hlen) {
-- 
2.17.1

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