diff options
| -rw-r--r-- | xen/include/public/io/netif.h | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/xen/include/public/io/netif.h b/xen/include/public/io/netif.h index ccde53b3af..9664998f05 100644 --- a/xen/include/public/io/netif.h +++ b/xen/include/public/io/netif.h @@ -31,6 +31,24 @@ #include "../grant_table.h" /* + * Older implementation of Xen network frontend / backend has an + * implicit dependency on the MAX_SKB_FRAGS as the maximum number of + * ring slots a skb can use. Netfront / netback may not work as + * expected when frontend and backend have different MAX_SKB_FRAGS. + * + * A better approach is to add mechanism for netfront / netback to + * negotiate this value. However we cannot fix all possible + * frontends, so we need to define a value which states the minimum + * slots backend must support. + * + * The minimum value derives from older Linux kernel's MAX_SKB_FRAGS + * (18), which is proved to work with most frontends. Any new backend + * which doesn't negotiate with frontend should expect frontend to + * send a valid packet using slots up to this value. + */ +#define XEN_NETIF_NR_SLOTS_MIN 18 + +/* * Notifications after enqueuing any type of message should be conditional on * the appropriate req_event or rsp_event field in the shared ring. * If the client sends notification for rx requests then it should specify |