Computer Science 853
                               Quiz 2        Name _________________


 1. Which of the following best characterizes a "shared" sk_buff.

    a. Multiple struct sk_buff's        b. A single struct sk_buff
       point to a single kmalloc'd         points to multiple kmalloc'd
       buffer area                         buffer areas

    c. Multiple entities hold valid
       pointers to a single struct
       sk_buff

 2. Which of the following best characterizes a "cloned" sk_buff.

    a. Multiple struct sk_buff's        b. A single struct sk_buff
       point to a single kmalloc'd         points to multiple kmalloc'd
       buffer area                         buffer areas

    c. Multiple entities hold valid
       pointers to a single struct
       sk_buff

 3. Describe consisely and precisely how "sharing" and "cloning" of
    an sk_buff affect the "users" and the "dataref" elements. (No
    effect is a legal but not necessarily correct answer).

    a new entity shares an sk_buff

       users -



       dataref -



    an sk_buff is cloned

       users -



       dataref -



 4. Identify the proper skb_* utility function that would be used
    to update appropriate buffer pointers and length fields when...

    a.  Appending user data to the buffer.




    b.  Inserting a new protocol header in an outgoing packet




    c. Removing a protocol header from a incoming packet.




 5. The value of skb->len should always be equal to:


    a. skb->end - skb->head          b. skb->end - skb->data


    c. skb->tail - skb->head         d. skb->tail - skb->data


 6. Pointers to the fragment list and  unmapped page buffers are kept in

    a. the struct sk_buff               b. the kmalloc'd area that is
                                           also used to hold header and
                                           application data.
    c. in an extra area that
       is also kmalloc'd.


7. Sleeping may occur in

   a. sock_alloc_send_skb() but         b. dev_alloc_skb() but not
      not dev_alloc_skb()                   sock_alloc_send_skb()

   c. neither                           d. both


8. When a Tx buffer is allocated the amount charged to the sock's
   wmem_alloc is:

   a. len                               b. data_len

   c. truesize


9. wmem_alloc is decremented

   a. as soon a the buffer is           b. as soon as the buffer is
      passed to the dev layer              added to the device's Tx ring

   c. only after the Tx complete
      interrupt associated with the
      transmission of the buffer


10. If two entities need for a buffer to reside on two different buffer
    lists the most efficient SAFE approach for doing this is:

    a. share the buffer                 b. clone the buffer

    c. make a complete copy
       of both header and data