/* Transmit routine used by generic_netmap_txsync(). Returns 0 on success
and -1 on error (which may be packet drops or other errors). */
int generic_xmit_frame(struct ifnet *ifp, struct mbuf *m,
void *addr, u_int len, u_int ring_nr)
{
netdev_tx_t ret;
/* Empty the sk_buff. */
if (unlikely(skb_headroom(m)))
skb_push(m, skb_headroom(m));
skb_trim(m, 0);
/* TODO Support the slot flags (NS_MOREFRAG, NS_INDIRECT). */
skb_copy_to_linear_data(m, addr, len); // skb_store_bits(m, 0, addr, len);
skb_put(m, len);
NM_ATOMIC_INC(&m->users);
m->dev = ifp;
/* Tell generic_ndo_start_xmit() to pass this mbuf to the driver. */
m->priority = NM_MAGIC_PRIORITY_TX;
skb_set_queue_mapping(m, ring_nr);
ret = dev_queue_xmit(m);
if (likely(ret == NET_XMIT_SUCCESS)) {
return 0;
}
if (unlikely(ret != NET_XMIT_DROP)) {
/* If something goes wrong in the TX path, there is nothing
intelligent we can do (for now) apart from error reporting. */
RD(5, "dev_queue_xmit failed: HARD ERROR %d", ret);
}
return -1;
}
/* Transmit routine used by generic_netmap_txsync(). Returns 0 on success
and -1 on error (which may be packet drops or other errors). */
int
nm_os_generic_xmit_frame(struct nm_os_gen_arg *a)
{
struct mbuf *m = a->m;
struct ifnet *ifp = a->ifp;
u_int len = a->len;
netdev_tx_t ret;
/* We know that the driver needs to prepend ifp->needed_headroom bytes
* to each packet to be transmitted. We then reset the mbuf pointers
* to the correct initial state:
* ___________________________________________
* ^ ^ ^
* | | |
* head data end
* tail
*
* which correspond to an empty buffer with exactly
* ifp->needed_headroom bytes between head and data.
*/
m->len = 0;
m->data = m->head + ifp->needed_headroom;
skb_reset_tail_pointer(m);
skb_reset_mac_header(m);
skb_reset_network_header(m);
/* Copy a netmap buffer into the mbuf.
* TODO Support the slot flags (NS_MOREFRAG, NS_INDIRECT). */
skb_copy_to_linear_data(m, a->addr, len); // skb_store_bits(m, 0, addr, len);
skb_put(m, len);
/* Hold a reference on this, we are going to recycle mbufs as
* much as possible. */
NM_ATOMIC_INC(&m->users);
/* On linux m->dev is not reliable, since it can be changed by the
* ndo_start_xmit() callback. This happens, for instance, with veth
* and bridge drivers. For this reason, the nm_os_generic_xmit_frame()
* implementation for linux stores a copy of m->dev into the
* destructor_arg field. */
m->dev = ifp;
skb_shinfo(m)->destructor_arg = m->dev;
/* Tell generic_ndo_start_xmit() to pass this mbuf to the driver. */
skb_set_queue_mapping(m, a->ring_nr);
m->priority = a->qevent ? NM_MAGIC_PRIORITY_TXQE : NM_MAGIC_PRIORITY_TX;
ret = dev_queue_xmit(m);
if (unlikely(ret != NET_XMIT_SUCCESS)) {
/* Reset priority, so that generic_netmap_tx_clean() can
* reclaim this mbuf. */
m->priority = 0;
/* Qdisc queue is full (this cannot happen with
* the netmap-aware qdisc, see exaplanation in
* netmap_generic_txsync), or qdisc is being
* deactivated. In the latter case dev_queue_xmit()
* does not call the enqueue method and returns
* NET_XMIT_DROP.
* If there is no carrier, the generic qdisc is
* not yet active (is pending in the qdisc_sleeping
* field), and so the temporary noop qdisc enqueue
* method will drop the packet and return NET_XMIT_CN.
*/
RD(3, "Warning: dev_queue_xmit() is dropping [%d]", ret);
return -1;
}
return 0;
}
