From f40bdbb80d59be824ee9cc9273785f9548a3fe77 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Beno=C3=AEt=20Ganne?= <bganne@cisco.com>
Date: Thu, 2 Dec 2021 16:06:12 +0100
Subject: [PATCH] af_xdp: make sure all packets are transmitted
MIME-Version: 1.0
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AF_XDP socket will only tx enqueued packets up to a max batch size so
we need to retry until everything has been sent.

Type: fix

Change-Id: Ia487ab63d3e85a478471cd1d679c5fb471804ba3
Signed-off-by: Benoît Ganne <bganne@cisco.com>
---
 src/plugins/af_xdp/input.c  |  4 +---
 src/plugins/af_xdp/output.c | 15 +++++++++++----
 2 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/src/plugins/af_xdp/input.c b/src/plugins/af_xdp/input.c
index 4f3ac5725a4..08b503b1641 100644
--- a/src/plugins/af_xdp/input.c
+++ b/src/plugins/af_xdp/input.c
@@ -15,7 +15,6 @@
  *------------------------------------------------------------------
  */
 
-#include <poll.h>
 #include <vlib/vlib.h>
 #include <vlib/unix/unix.h>
 #include <vlib/pci/pci.h>
@@ -89,8 +88,7 @@ af_xdp_device_input_refill_db (vlib_main_t * vm,
 
   if (clib_spinlock_trylock_if_init (&rxq->syscall_lock))
     {
-      struct pollfd fd = { .fd = rxq->xsk_fd, .events = POLLIN | POLLOUT };
-      int ret = poll (&fd, 1, 0);
+      int ret = recvmsg (rxq->xsk_fd, 0, MSG_DONTWAIT);
       clib_spinlock_unlock_if_init (&rxq->syscall_lock);
       if (PREDICT_FALSE (ret < 0))
 	{
diff --git a/src/plugins/af_xdp/output.c b/src/plugins/af_xdp/output.c
index d1500a63cbb..8136d918a75 100644
--- a/src/plugins/af_xdp/output.c
+++ b/src/plugins/af_xdp/output.c
@@ -1,4 +1,3 @@
-#include <poll.h>
 #include <string.h>
 #include <vlib/vlib.h>
 #include <vlib/unix/unix.h>
@@ -101,11 +100,19 @@ af_xdp_device_output_tx_db (vlib_main_t * vm,
 
   if (xsk_ring_prod__needs_wakeup (&txq->tx))
     {
-      struct pollfd fd = { .fd = txq->xsk_fd, .events = POLLIN | POLLOUT };
-      int ret = poll (&fd, 1, 0);
+      const struct msghdr msg = {};
+      int ret;
+      /* On tx, xsk socket will only tx up to TX_BATCH_SIZE, as defined in
+       * kernel net/xdp/xsk.c. Unfortunately we do not know how much this is,
+       * our only option is to retry until everything is sent... */
+      do
+	{
+	  ret = sendmsg (txq->xsk_fd, &msg, MSG_DONTWAIT);
+	}
+      while (ret < 0 && EAGAIN == errno);
       if (PREDICT_FALSE (ret < 0))
 	{
-	  /* something bad is happening */
+	  /* not EAGAIN: something bad is happening */
 	  vlib_error_count (vm, node->node_index,
 			    AF_XDP_TX_ERROR_SYSCALL_FAILURES, 1);
 	  af_xdp_device_error (ad, "tx poll() failed");