On Mon, Oct 21, 2024 at 4:21 PM Jason Wang <jasow...@redhat.com> wrote:
>
> On Sun, Sep 15, 2024 at 9:07 AM Akihiko Odaki <akihiko.od...@daynix.com>
> wrote:
> >
> > receive_header() used to cast the const qualifier of the pointer to the
> > received packet away to modify the header. Avoid this by copying the
> > received header to buffer.
> >
> > Signed-off-by: Akihiko Odaki <akihiko.od...@daynix.com>
> > ---
> > hw/net/virtio-net.c | 85
> > +++++++++++++++++++++++++++++------------------------
> > 1 file changed, 46 insertions(+), 39 deletions(-)
> >
> > diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> > index 3fc1d10cb9e0..ca4e22344f78 100644
> > --- a/hw/net/virtio-net.c
> > +++ b/hw/net/virtio-net.c
> > @@ -1685,41 +1685,44 @@ static void virtio_net_hdr_swap(VirtIODevice *vdev,
> > struct virtio_net_hdr *hdr)
> > * cache.
> > */
> > static void work_around_broken_dhclient(struct virtio_net_hdr *hdr,
> > - uint8_t *buf, size_t size)
> > + size_t *hdr_len, const uint8_t
> > *buf,
> > + size_t buf_size, size_t
> > *buf_offset)
> > {
> > size_t csum_size = ETH_HLEN + sizeof(struct ip_header) +
> > sizeof(struct udp_header);
> >
> > + buf += *buf_offset;
> > + buf_size -= *buf_offset;
> > +
> > if ((hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) && /* missing csum */
> > - (size >= csum_size && size < 1500) && /* normal sized MTU */
> > + (buf_size >= csum_size && buf_size < 1500) && /* normal sized MTU
> > */
> > (buf[12] == 0x08 && buf[13] == 0x00) && /* ethertype == IPv4 */
> > (buf[23] == 17) && /* ip.protocol == UDP */
> > (buf[34] == 0 && buf[35] == 67)) { /* udp.srcport == bootps */
> > - net_checksum_calculate(buf, size, CSUM_UDP);
> > + memcpy((uint8_t *)hdr + *hdr_len, buf, csum_size);
> > + net_checksum_calculate((uint8_t *)hdr + *hdr_len, csum_size,
> > CSUM_UDP);
> > hdr->flags &= ~VIRTIO_NET_HDR_F_NEEDS_CSUM;
> > + *hdr_len += csum_size;
> > + *buf_offset += csum_size;
> > }
> > }
> >
> > -static void receive_header(VirtIONet *n, const struct iovec *iov, int
> > iov_cnt,
> > - const void *buf, size_t size)
> > +static size_t receive_header(VirtIONet *n, struct virtio_net_hdr *hdr,
> > + const void *buf, size_t buf_size,
> > + size_t *buf_offset)
> > {
> > - if (n->has_vnet_hdr) {
> > - /* FIXME this cast is evil */
> > - void *wbuf = (void *)buf;
> > - work_around_broken_dhclient(wbuf, wbuf + n->host_hdr_len,
> > - size - n->host_hdr_len);
> > + size_t hdr_len = n->guest_hdr_len;
> >
> > - if (n->needs_vnet_hdr_swap) {
> > - virtio_net_hdr_swap(VIRTIO_DEVICE(n), wbuf);
> > - }
> > - iov_from_buf(iov, iov_cnt, 0, buf, sizeof(struct virtio_net_hdr));
> > - } else {
> > - struct virtio_net_hdr hdr = {
> > - .flags = 0,
> > - .gso_type = VIRTIO_NET_HDR_GSO_NONE
> > - };
> > - iov_from_buf(iov, iov_cnt, 0, &hdr, sizeof hdr);
> > + memcpy(hdr, buf, sizeof(struct virtio_net_hdr));
> > +
> > + *buf_offset = n->host_hdr_len;
> > + work_around_broken_dhclient(hdr, &hdr_len, buf, buf_size, buf_offset);
> > +
> > + if (n->needs_vnet_hdr_swap) {
> > + virtio_net_hdr_swap(VIRTIO_DEVICE(n), hdr);
> > }
> > +
> > + return hdr_len;
> > }
> >
> > static int receive_filter(VirtIONet *n, const uint8_t *buf, int size)
> > @@ -1887,6 +1890,13 @@ static int virtio_net_process_rss(NetClientState
> > *nc, const uint8_t *buf,
> > return (index == new_index) ? -1 : new_index;
> > }
> >
> > +typedef struct Header {
> > + struct virtio_net_hdr_v1_hash virtio_net;
> > + struct eth_header eth;
> > + struct ip_header ip;
> > + struct udp_header udp;
> > +} Header;
>
> I don't see too much value in having this structure especially
> considering eth/ip/udp is not even used.
>
> Any reason we can simply use an array as a buffer in virtio_net_receive_rcu()?
Btw, since the code was for ancient guests and userspace, I wonder how
it is tested.
Thanks
>
> Thanks
