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AF_XDP-interaction: workaround for detecting when AF_XDP is read for TX

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I hope there exist a better API for determining when AF_XDP
is ready for transmitting packets.

This workaround keeps trying to send a single packet, and
check return value seen from sendto() syscall, until it
doesn't return an error.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
This commit is contained in:
Jesper Dangaard Brouer
2022-01-14 16:48:13 +01:00
parent 6d6ac23f3b
commit 86b76f564f
1 changed files with 20 additions and 7 deletions
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27
AF_XDP-interaction/af_xdp_user.c
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@@ -538,20 +538,24 @@ static int kick_tx(struct xsk_socket_info *xsk)
__func__, errno);
err = errno;
}
/* Kernel samples/bpf/ xdp_sock_user.c kick_tx variant doesn't
* treat the following errno values as errors:
* ENOBUFS , EAGAIN , EBUSY , ENETDOWN
*/
return err;
}
static void complete_tx(struct xsk_socket_info *xsk)
static int complete_tx(struct xsk_socket_info *xsk)
{
unsigned int completed;
uint32_t idx_cq;
int ret;
int err;
if (!xsk->outstanding_tx)
return;
/* Notify kernel via sendto syscall that TX packet are avail */
kick_tx(xsk);
err = kick_tx(xsk);
/* Collect/free completed TX buffers */
completed = xsk_ring_cons__peek(&xsk->cq,
@@ -577,6 +581,8 @@ static void complete_tx(struct xsk_socket_info *xsk)
xsk->outstanding_tx -= completed < xsk->outstanding_tx ?
completed : xsk->outstanding_tx;
}
return err;
}
static inline __sum16 csum16_add(__sum16 csum, __be16 addend)
@@ -863,7 +869,7 @@ static void print_pkt_info(uint8_t *pkt, uint32_t len)
}
}
static void tx_pkt(struct config *cfg, struct xsk_socket_info *xsk)
static int tx_pkt(struct config *cfg, struct xsk_socket_info *xsk)
{
struct xsk_umem_info *umem = xsk->umem;
uint64_t pkt_addr = mem_alloc_umem_frame(&umem->mem);
@@ -893,7 +899,8 @@ static void tx_pkt(struct config *cfg, struct xsk_socket_info *xsk)
xsk_ring_prod__submit(&xsk->tx, 1);
xsk->outstanding_tx++;
}
complete_tx(xsk);
return complete_tx(xsk);
}
/* Generate some fake packets (in umem area). Real system will deliver TX
@@ -1640,9 +1647,15 @@ int main(int argc, char **argv)
* It seems related with XDP attachment causing link down/up event for
* some drivers. Q: What is the right method/API that waits for link to
* be initilized correctly?
*
* This workaround keeps trying to send a single packet, and
* check return value seen from sendto() syscall, until it
* doesn't return an error.
*/
//sleep(3);
tx_pkt(&cfg, xsks.sockets[0]);
while (err = tx_pkt(&cfg, xsks.sockets[0])) {
fprintf(stderr, "WARN(%d): Failed to Tx pkt, will retry\n", err);
sleep(1);
}
/* Receive and count packets than drop them */
// rx_and_process(&cfg, &xsks);