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vmac: fix creation / deletion VMAC issue due to race conditions #2388

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Commits on Feb 23, 2024

  1. netlink: fix vmac deletion issue due to race condition

    Due to a race condition, the VMAC interface sometimes remains undeleted
    after Netlink reports the removal of its link interface.
    
    The function cleanup_lost_interface() fails to delete the interface.
    This failure occurs because the condition
    'IF_BASE_IFP(vrrp->ifp) != ifp' in the following code segment never
    matches:
    
    > 		if (vrrp->ifp != ifp
    > #ifdef _HAVE_VRRP_VMAC_
    > 		    && IF_BASE_IFP(vrrp->ifp) != ifp && VRRP_CONFIGURED_IFP(vrrp) != ifp
    > #endif
    
    This non-matching situation arises because 'vrrp->ifp->base_ifp' is the
    same as 'vrrp->ifp'.
    
    During the initialization in if_get_by_ifname(), when a new interface_t
    pointer is created, 'ifp->base_ifp' is set as follows:
    
    > ifp->base_ifp = ifp;
    
    netlink_if_link_populate() gets bypassed whenever
    'ifp->base_ifp->ifindex' is different from the index of the actual link
    interface. This bypass is inevitable when 'ifp' is newly allocated.
    netlink_if_link_populate() normally populates the 'ifp' data including
    the 'ifp->base_ifp'.
    
    Fix the issue of VMAC deletion by adjusting the logic so that
    netlink_if_link_populate() does not get skipped when the base_ifp of a
    VMAC is the VMAC itself.
    
    Signed-off-by: Louis Scalbert <[email protected]>
    louis-6wind committed Feb 23, 2024
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  2. netlink: add endif descriptions in netlink_if_link_populate()

    Add #endif descriptions in netlink_if_link_populate() to clarify in
    which #ifdef blocks the next commit is modifying the code. This is a
    cosmetic change.
    
    Signed-off-by: Louis Scalbert <[email protected]>
    louis-6wind committed Feb 23, 2024
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  3. vrrp: fix vmac creation issue due to race condition

    The VMAC interface sometimes does not reappear when its associated link
    interface is quickly re-added after being deleted, a situation caused by
    a race condition.
    
    This problem manifests during the operations of cleanup_lost_interface()
    This function checks for VMAC interfaces on top of the removed link
    interface. It deletes these VMAC interfaces if they are present.
    Subsequently, Netlink is invoked to refresh the information of all
    interfaces, and this is followed by the cleaning of the link interface
    data in memory.
    
    The problem occurs when Netlink, queried indirectly by sub-functions of
    cleanup_lost_interface(), detects that the link interface has
    reappeared. Although the interface data in memory is updated
    accordingly, cleanup_lost_interface() unconditionally clears this
    refreshed information. As a result, the data regarding the link
    interface is lost, preventing the re-creation of its associated
    VMAC interfaces.
    
    Fix the VMAC creation issue by adding a 'cleaning flag' that is set at
    the start of the cleanup process. This flag says whether to proceed with
    the interface data cleanup. If the interface is refreshed during the
    Netlink polling, the flag is unset, thereby preventing the subsequent
    clearing of the updated interface information.
    
    Signed-off-by: Louis Scalbert <[email protected]>
    louis-6wind committed Feb 23, 2024
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