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Message-ID: <f860d6a2-12a4-c766-ee57-db789c4a8d1f@redhat.com>
Date: Thu, 24 Jun 2021 14:18:08 +0800
From: Jason Wang <jasowang@...hat.com>
To: David Woodhouse <dwmw2@...radead.org>, netdev@...r.kernel.org
Cc: Eugenio Pérez <eperezma@...hat.com>
Subject: Re: [PATCH v2 1/4] net: tun: fix tun_xdp_one() for IFF_TUN mode
在 2021/6/23 下午9:52, David Woodhouse 写道:
> On Wed, 2021-06-23 at 11:45 +0800, Jason Wang wrote:
>> As replied in previous version, it would be better if we can unify
>> similar logic in tun_get_user().
> So that ends up looking something like this (incremental).
>
> Note the '/* XXX: frags && */' part in tun_skb_set_protocol(), because
> the 'frags &&' was there in tun_get_user() and it wasn't obvious to me
> whether I should be lifting that out as a separate argument to
> tun_skb_set_protocol() or if there's a better way.
>
> Either way, in my judgement this is less suitable for a stable fix and
> more appropriate for a follow-on cleanup. But I don't feel that
> strongly; I'm more than happy for you to overrule me on that.
> Especially if you fix the above XXX part while you're at it :)
By simply adding a boolean "pull" in tun_skb_set_protocol()?
Thanks
>
> I tested this with vhost-net and !IFF_NO_PI, and TX works. RX is still
> hosed on the vhost-net side, for the same reason that a bunch of test
> cases were already listed in #if 0, but I'll address that in a separate
> email. It's not part of *this* patch.
>
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -1641,6 +1641,40 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
> return NULL;
> }
>
> +static int tun_skb_set_protocol(struct tun_struct *tun, struct sk_buff *skb,
> + __be16 pi_proto)
> +{
> + switch (tun->flags & TUN_TYPE_MASK) {
> + case IFF_TUN:
> + if (tun->flags & IFF_NO_PI) {
> + u8 ip_version = skb->len ? (skb->data[0] >> 4) : 0;
> +
> + switch (ip_version) {
> + case 4:
> + pi_proto = htons(ETH_P_IP);
> + break;
> + case 6:
> + pi_proto = htons(ETH_P_IPV6);
> + break;
> + default:
> + return -EINVAL;
> + }
> + }
> +
> + skb_reset_mac_header(skb);
> + skb->protocol = pi_proto;
> + skb->dev = tun->dev;
> + break;
> + case IFF_TAP:
> + if (/* XXX frags && */!pskb_may_pull(skb, ETH_HLEN))
> + return -ENOMEM;
> +
> + skb->protocol = eth_type_trans(skb, tun->dev);
> + break;
> + }
> + return 0;
> +}
> +
> /* Get packet from user space buffer */
> static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
> void *msg_control, struct iov_iter *from,
> @@ -1784,37 +1818,9 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
> return -EINVAL;
> }
>
> - switch (tun->flags & TUN_TYPE_MASK) {
> - case IFF_TUN:
> - if (tun->flags & IFF_NO_PI) {
> - u8 ip_version = skb->len ? (skb->data[0] >> 4) : 0;
> -
> - switch (ip_version) {
> - case 4:
> - pi.proto = htons(ETH_P_IP);
> - break;
> - case 6:
> - pi.proto = htons(ETH_P_IPV6);
> - break;
> - default:
> - atomic_long_inc(&tun->dev->rx_dropped);
> - kfree_skb(skb);
> - return -EINVAL;
> - }
> - }
> -
> - skb_reset_mac_header(skb);
> - skb->protocol = pi.proto;
> - skb->dev = tun->dev;
> - break;
> - case IFF_TAP:
> - if (frags && !pskb_may_pull(skb, ETH_HLEN)) {
> - err = -ENOMEM;
> - goto drop;
> - }
> - skb->protocol = eth_type_trans(skb, tun->dev);
> - break;
> - }
> + err = tun_skb_set_protocol(tun, skb, pi.proto);
> + if (err)
> + goto drop;
>
> /* copy skb_ubuf_info for callback when skb has no error */
> if (zerocopy) {
> @@ -2334,8 +2340,10 @@ static int tun_xdp_one(struct tun_struct *tun,
> struct virtio_net_hdr *gso = NULL;
> struct bpf_prog *xdp_prog;
> struct sk_buff *skb = NULL;
> + __be16 proto = 0;
> u32 rxhash = 0, act;
> int buflen = hdr->buflen;
> + int reservelen = xdp->data - xdp->data_hard_start;
> int err = 0;
> bool skb_xdp = false;
> struct page *page;
> @@ -2343,6 +2351,17 @@ static int tun_xdp_one(struct tun_struct *tun,
> if (tun->flags & IFF_VNET_HDR)
> gso = &hdr->gso;
>
> + if (!(tun->flags & IFF_NO_PI)) {
> + struct tun_pi *pi = xdp->data;
> + if (datasize < sizeof(*pi)) {
> + atomic_long_inc(&tun->rx_frame_errors);
> + return -EINVAL;
> + }
> + proto = pi->proto;
> + reservelen += sizeof(*pi);
> + datasize -= sizeof(*pi);
> + }
> +
> xdp_prog = rcu_dereference(tun->xdp_prog);
> if (xdp_prog) {
> if (gso && gso->gso_type) {
> @@ -2388,8 +2407,8 @@ static int tun_xdp_one(struct tun_struct *tun,
> goto out;
> }
>
> - skb_reserve(skb, xdp->data - xdp->data_hard_start);
> - skb_put(skb, xdp->data_end - xdp->data);
> + skb_reserve(skb, reservelen);
> + skb_put(skb, datasize);
>
> if (gso && virtio_net_hdr_to_skb(skb, gso, tun_is_little_endian(tun))) {
> atomic_long_inc(&tun->rx_frame_errors);
> @@ -2397,48 +2416,12 @@ static int tun_xdp_one(struct tun_struct *tun,
> err = -EINVAL;
> goto out;
> }
> - switch (tun->flags & TUN_TYPE_MASK) {
> - case IFF_TUN:
> - if (tun->flags & IFF_NO_PI) {
> - u8 ip_version = skb->len ? (skb->data[0] >> 4) : 0;
>
> - switch (ip_version) {
> - case 4:
> - skb->protocol = htons(ETH_P_IP);
> - break;
> - case 6:
> - skb->protocol = htons(ETH_P_IPV6);
> - break;
> - default:
> - atomic_long_inc(&tun->dev->rx_dropped);
> - kfree_skb(skb);
> - err = -EINVAL;
> - goto out;
> - }
> - } else {
> - struct tun_pi *pi = (struct tun_pi *)skb->data;
> - if (!pskb_may_pull(skb, sizeof(*pi))) {
> - atomic_long_inc(&tun->dev->rx_dropped);
> - kfree_skb(skb);
> - err = -ENOMEM;
> - goto out;
> - }
> - skb_pull_inline(skb, sizeof(*pi));
> - skb->protocol = pi->proto;
> - }
> -
> - skb_reset_mac_header(skb);
> - skb->dev = tun->dev;
> - break;
> - case IFF_TAP:
> - if (!pskb_may_pull(skb, ETH_HLEN)) {
> - atomic_long_inc(&tun->dev->rx_dropped);
> - kfree_skb(skb);
> - err = -ENOMEM;
> - goto out;
> - }
> - skb->protocol = eth_type_trans(skb, tun->dev);
> - break;
> + err = tun_skb_set_protocol(tun, skb, proto);
> + if (err) {
> + atomic_long_inc(&tun->dev->rx_dropped);
> + kfree_skb(skb);
> + goto out;
> }
>
> skb_reset_network_header(skb);
>
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