net/af-xdp: Remove XDP program cleanup logic

There are two issues with the XDP program removal in af_xdp_cleanup():

1) Starting from libxdp 1.3.0 [0] the XDP program gets automatically
   detached when we call xsk_socket__delete() for the last successfully
   configured queue. libxdp internally keeps track of that. For QEMU
   we require libxdp >= 1.4.0. Given QEMU is not loading the program,
   lets also not attempt to remove it and delegate this instead.

2) The removal logic is incorrect anyway because we are setting n_queues
   into the last queue that never has xdp_flags on failure, so the logic
   is always skipped since the non-zero test for s->xdp_flags in
   af_xdp_cleanup() fails.

Fixes: cb039ef3d9e3 ("net: add initial support for AF_XDP network backend")
Suggested-by: Ilya Maximets <i.maximets@ovn.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Ilya Maximets <i.maximets@ovn.org>
Cc: Ilya Maximets <i.maximets@ovn.org>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Anton Protopopov <aspsk@isovalent.com>
Link: https://github.com/xdp-project/xdp-tools/commit/38c2914988fd5c1ef65f2381fc8af9f3e8404e2b
Signed-off-by: Jason Wang <jasowang@redhat.com>

diff --git a/net/af-xdp.c b/net/af-xdp.c
index d022534d764e7c34b16e60c05a4763e35abca169..3d3268e18bb976a28afe43883d147bd9adc8dbb2 100644 (file)
--- a/net/af-xdp.c
+++ b/net/af-xdp.c
@@ -49,7 +49,6 @@ typedef struct AFXDPState {
     char                 *buffer;
     struct xsk_umem      *umem;
 
-    uint32_t             n_queues;
     uint32_t             xdp_flags;
     bool                 inhibit;
 } AFXDPState;
@@ -274,14 +273,6 @@ static void af_xdp_cleanup(NetClientState *nc)
     s->umem = NULL;
     qemu_vfree(s->buffer);
     s->buffer = NULL;
-
-    /* Remove the program if it's the last open queue. */
-    if (!s->inhibit && nc->queue_index == s->n_queues - 1 && s->xdp_flags
-        && bpf_xdp_detach(s->ifindex, s->xdp_flags, NULL) != 0) {
-        fprintf(stderr,
-                "af-xdp: unable to remove XDP program from '%s', ifindex: %d\n",
-                s->ifname, s->ifindex);
-    }
 }
 
 static int af_xdp_umem_create(AFXDPState *s, int sock_fd, Error **errp)
@@ -490,12 +481,9 @@ int net_init_af_xdp(const Netdev *netdev,
 
         pstrcpy(s->ifname, sizeof(s->ifname), opts->ifname);
         s->ifindex = ifindex;
-        s->n_queues = queues;
 
         if (af_xdp_umem_create(s, sock_fds ? sock_fds[i] : -1, errp)
             || af_xdp_socket_create(s, opts, errp)) {
-            /* Make sure the XDP program will be removed. */
-            s->n_queues = i;
             error_propagate(errp, err);
             goto err;
         }