Messages in this thread | | | Date | Mon, 9 Dec 2013 12:56:38 +0200 | From | "Michael S. Tsirkin" <> | Subject | Re: [PATCH net 1/2] tun: unbreak truncated packet signalling |
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On Mon, Dec 09, 2013 at 12:55:29PM +0200, Michael S. Tsirkin wrote: > On Mon, Dec 09, 2013 at 06:25:16PM +0800, Jason Wang wrote: > > Commit 6680ec68eff47d36f67b4351bc9836fd6cba9532 > > (tuntap: hardware vlan tx support) breaks the truncated packet signal by never > > return a length greater than iov length in tun_put_user(). This patch fixes this > > by always return the length of packet plus possible vlan header. Caller can > > detect the truncated packet by comparing the return value and the size of iov > > length. > > > > Reported-by: Vlad Yasevich <vyasevich@gmail.com> > > Cc: Vlad Yasevich <vyasevich@gmail.com> > > Cc: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com> > > Signed-off-by: Jason Wang <jasowang@redhat.com> > > So writer gets back a value greater than what was written?
Pls ignore this question - wrote it before I understood the patch, and forgot to remove. The rest of the comments and the proposed alternative patch still stand.
> > --- > > The patch is needed for stable. > > --- > > drivers/net/tun.c | 23 ++++++++++++----------- > > 1 file changed, 12 insertions(+), 11 deletions(-) > > > > diff --git a/drivers/net/tun.c b/drivers/net/tun.c > > index e26cbea..dd1bd7a 100644 > > --- a/drivers/net/tun.c > > +++ b/drivers/net/tun.c > > @@ -1183,7 +1183,11 @@ static ssize_t tun_put_user(struct tun_struct *tun, > > const struct iovec *iv, int len) > > { > > struct tun_pi pi = { 0, skb->protocol }; > > - ssize_t total = 0; > > + struct { > > + __be16 h_vlan_proto; > > + __be16 h_vlan_TCI; > > + } veth; > > + ssize_t total = 0, off = 0; > > Why off = 0 here? > We initialize it to total unconditionally, don't we? > > > int vlan_offset = 0; > > > > if (!(tun->flags & TUN_NO_PI)) { > > @@ -1248,14 +1252,11 @@ static ssize_t tun_put_user(struct tun_struct *tun, > > total += tun->vnet_hdr_sz; > > } > > > > + off = total; > > if (!vlan_tx_tag_present(skb)) { > > len = min_t(int, skb->len, len); > > } else { > > int copy, ret; > > - struct { > > - __be16 h_vlan_proto; > > - __be16 h_vlan_TCI; > > - } veth; > > > > veth.h_vlan_proto = skb->vlan_proto; > > veth.h_vlan_TCI = htons(vlan_tx_tag_get(skb)); > > @@ -1264,22 +1265,22 @@ static ssize_t tun_put_user(struct tun_struct *tun, > > len = min_t(int, skb->len + VLAN_HLEN, len); > > > > copy = min_t(int, vlan_offset, len); > > - ret = skb_copy_datagram_const_iovec(skb, 0, iv, total, copy); > > + ret = skb_copy_datagram_const_iovec(skb, 0, iv, off, copy); > > len -= copy; > > - total += copy; > > + off += copy; > > if (ret || !len) > > goto done; > > > > copy = min_t(int, sizeof(veth), len); > > - ret = memcpy_toiovecend(iv, (void *)&veth, total, copy); > > + ret = memcpy_toiovecend(iv, (void *)&veth, off, copy); > > len -= copy; > > - total += copy; > > + off += copy; > > if (ret || !len) > > goto done; > > This seems wrong: if one of the branches above is taken, total is > never incremented. > > > } > > > > - skb_copy_datagram_const_iovec(skb, vlan_offset, iv, total, len); > > - total += len; > > + skb_copy_datagram_const_iovec(skb, vlan_offset, iv, off, len); > > + total += skb->len + (vlan_offset ? sizeof(veth) : 0); > > > > done: > > tun->dev->stats.tx_packets++; > > I also think it's inelegant that the veth struct is now in the > outside scope, and the extra ? is also ugly. > > Here's a smaller patch to fix all these problems - what do you think? > > > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > > --- > > diff --git a/drivers/net/tun.c b/drivers/net/tun.c > index 782e38b..3297e41 100644 > --- a/drivers/net/tun.c > +++ b/drivers/net/tun.c > @@ -1183,7 +1183,7 @@ static ssize_t tun_put_user(struct tun_struct *tun, > const struct iovec *iv, int len) > { > struct tun_pi pi = { 0, skb->protocol }; > - ssize_t total = 0; > + ssize_t total = 0, offset; > int vlan_offset = 0; > > if (!(tun->flags & TUN_NO_PI)) { > @@ -1248,6 +1248,8 @@ static ssize_t tun_put_user(struct tun_struct *tun, > total += tun->vnet_hdr_sz; > } > > + offset = total; > + total += skb->len; > if (!vlan_tx_tag_present(skb)) { > len = min_t(int, skb->len, len); > } else { > @@ -1257,6 +1259,8 @@ static ssize_t tun_put_user(struct tun_struct *tun, > __be16 h_vlan_TCI; > } veth; > > + total += sizeof(veth); > + > veth.h_vlan_proto = skb->vlan_proto; > veth.h_vlan_TCI = htons(vlan_tx_tag_get(skb)); > > @@ -1279,7 +1283,6 @@ static ssize_t tun_put_user(struct tun_struct *tun, > } > > skb_copy_datagram_const_iovec(skb, vlan_offset, iv, total, len); > - total += len; > > done: > tun->dev->stats.tx_packets++; > > > -- > > 1.8.3.2
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