Thomas Schwinge, le Sat 22 Nov 2008 22:54:21 +0100, a écrit :
> > believing
> > that the IP stack wouldn't overcome the typical 1500B MTU anyway.
>
> It will, because you told it can do so, allowing for a PAGE_SIZE MTU.
> But: The MTU is defined to be without the ethernet headers, thus pfinet
> can create ethernet frames that are bigger than a page.
Ah, ok.
> Here is a fix. OK to be committed?
>
> Index: xen/net.c
> ===================================================================
> RCS file: /cvsroot/hurd/gnumach/xen/Attic/net.c,v
> retrieving revision 1.1.2.36
> diff -u -p -r1.1.2.36 net.c
> --- xen/net.c 22 Sep 2008 18:49:56 -0000 1.1.2.36
> +++ xen/net.c 22 Nov 2008 21:48:22 -0000
> @@ -383,9 +383,10 @@ void hyp_net_init(void) {
> ifp = &nd->ifnet;
> ifp->if_unit = n;
> ifp->if_flags = IFF_UP | IFF_RUNNING;
> - ifp->if_mtu = PAGE_SIZE;
> ifp->if_header_size = 14;
> ifp->if_header_format = HDR_ETHERNET;
> + /* Set to the maximum that we can handle in device_write. */
> + ifp->if_mtu = PAGE_SIZE - ifp->if_header_size;
That's fine yes.
> Additionally, I'd suggest this change to better (?) explain what we're
> doing (and align to the other network device_write implementations).
>
> Index: xen/net.c
> ===================================================================
> RCS file: /cvsroot/hurd/gnumach/xen/Attic/net.c,v
> retrieving revision 1.1.2.36
> diff -u -p -r1.1.2.36 net.c
> --- xen/net.c 22 Sep 2008 18:49:56 -0000 1.1.2.36
> +++ xen/net.c 22 Nov 2008 21:48:22 -0000
> @@ -483,13 +484,15 @@ device_write(void *d, ipc_port_t reply_p
> vm_map_copy_t copy = (vm_map_copy_t) data;
> grant_ref_t gref;
> struct net_data *nd = d;
> + struct ifnet *ifp = &nd->ifnet;
> netif_tx_request_t *req;
> unsigned reqn;
> vm_offset_t offset;
> vm_page_t m;
> vm_size_t size;
>
> - if (count == 0 || count > PAGE_SIZE)
> + if (count < ifp->if_header_size ||
> + count > ifp->if_header_size + ifp->if_mtu)
> return D_INVALID_SIZE;
>
> assert(copy->type == VM_MAP_COPY_PAGE_LIST);
Mmm, the < should be fine, but I'd rather see the > still use PAGE_SIZE,
or perhaps replace these PAGE_SIZE occurrences with a macro defed to
PAGE_SIZE.
Samuel
