if_wg: use proper barriers around pkt->p_state
Without appropriate load-synchronization to pair with store barriers in wg_encrypt() and wg_decrypt(), the compiler and hardware are often allowed to reorder these loads in wg_deliver_out() and wg_deliver_in() such that we end up with a garbage or intermediate mbuf that we try to pass on. The issue is particularly prevalent with the weaker memory models of !x86 platforms. Switch from the big-hammer wmb() to more explicit acq/rel atomics to both make it obvious what we're syncing up with, and to avoid somewhat hefty fences on platforms that don't necessarily need this. With this patch, my dual-iperf3 reproducer is dramatically more stable than it is without on aarch64. PR: 264115 Reviewed by: andrew, zlei (cherry picked from commit 3705d679a6344c957cae7a1b6372a8bfb8c44f0e)
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@ -1519,8 +1519,7 @@ wg_encrypt(struct wg_softc *sc, struct wg_packet *pkt)
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state = WG_PACKET_CRYPTED;
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out:
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pkt->p_mbuf = m;
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wmb();
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pkt->p_state = state;
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atomic_store_rel_int(&pkt->p_state, state);
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GROUPTASK_ENQUEUE(&peer->p_send);
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noise_remote_put(remote);
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}
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@ -1592,8 +1591,7 @@ wg_decrypt(struct wg_softc *sc, struct wg_packet *pkt)
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state = WG_PACKET_CRYPTED;
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out:
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pkt->p_mbuf = m;
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wmb();
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pkt->p_state = state;
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atomic_store_rel_int(&pkt->p_state, state);
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GROUPTASK_ENQUEUE(&peer->p_recv);
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noise_remote_put(remote);
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}
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@ -1649,7 +1647,7 @@ wg_deliver_out(struct wg_peer *peer)
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wg_peer_get_endpoint(peer, &endpoint);
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while ((pkt = wg_queue_dequeue_serial(&peer->p_encrypt_serial)) != NULL) {
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if (pkt->p_state != WG_PACKET_CRYPTED)
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if (atomic_load_acq_int(&pkt->p_state) != WG_PACKET_CRYPTED)
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goto error;
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m = pkt->p_mbuf;
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@ -1713,7 +1711,7 @@ wg_deliver_in(struct wg_peer *peer)
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int af;
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while ((pkt = wg_queue_dequeue_serial(&peer->p_decrypt_serial)) != NULL) {
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if (pkt->p_state != WG_PACKET_CRYPTED)
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if (atomic_load_acq_int(&pkt->p_state) != WG_PACKET_CRYPTED)
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goto error;
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m = pkt->p_mbuf;
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