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Subject[RFC PATCH 6/7] tun: populate hash in virtio-net header when needed
Date
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.benditovich@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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