netgraph memory trouble

From: David Vos (david.vos_at_gmail.com)
Date: 08/18/05

  • Next message: Donatas: "Re: multiple interfaces" 
    Date: Thu, 18 Aug 2005 15:43:32 -0600
To: freebsd-net@freebsd.org

    I have been playing with the netgraph ng_split node. I discovered
    that if I sent packets to it, after a period of time, I could no
    longer use netgraph. If I tried to use ngctl, I got an error back
    saying that it could not allocate memory to send a message. This also
    meant that I could not shutdown my nodes (because that required
    sending a message) and had to reboot my machine to start using
    netgraph again.

    vmstat -m would show netgraph_item having 128 items in use.

    I am sending data to the split node using the macro
    "NG_FWD_ITEM_HOOK". Since this macro nulls out the item pointer, I
    assume it takes full responsibility to free the item if something
    fails.

    The item then gets sent on to the function:
    static int
    ng_split_rcvdata(hook_p hook, item_p item)
    {
            const priv_p priv = NG_NODE_PRIVATE(NG_HOOK_NODE(hook));
            int error = 0;

            if (hook == priv->out) {
                    printf("ng_split: got packet from out hook!\n");
                    NG_FREE_ITEM(item);
                    error = EINVAL;
            } else if ((hook == priv->in) && (priv->mixed != NULL)) {
                    NG_FWD_ITEM_HOOK(error, item, priv->mixed);
            } else if ((hook == priv->mixed) && (priv->out != NULL)) {
                    NG_FWD_ITEM_HOOK(error, item, priv->out);
            }

            return (error);
    }

    Unfortunately, if priv->mixed or priv->out are NULL, then there is no
    error generated, and the item is not freed.

    I modified the function to be:
            printf("ng_split: got packet hook=%x, priv->in=%x, priv->out=%x
                       priv->mixed=%x\n", hook, priv->in, priv->out, priv->mixed);

            if (hook == priv->out) {
                    printf("ng_split: got packet from out hook!\n");
                    NG_FREE_ITEM(item);
                    error = EINVAL;
            } else if ((hook == priv->in) && (priv->mixed != NULL)) {
                    NG_FWD_ITEM_HOOK(error, item, priv->mixed);
            } else if ((hook == priv->mixed) && (priv->out != NULL)) {
                    NG_FWD_ITEM_HOOK(error, item, priv->out);
            } else {
                    printf("ng_split: got packet from unknown hook, or
    output hook is null\n");
                    NG_FREE_ITEM(item);
                    error = EINVAL;
            }

    In /var/log/messages, I get:
    Aug 18 15:31:50 foo kernel: ng_split: got packet hook=c53f6800,
    priv->in=c53f6800, priv->out=c53f8c80 priv->mixed=0
    Aug 18 15:31:50 foo kernel: ng_split: got packet from unknown hook, or
    output hook is null

    After making this modification to the code, I have not experienced any
    of the memory problems mentioned above.

    My conclusion is that an else clause needs to be added to the branches
    in the ng_split_rcfdata() function.

    I am using FreeBSD 5.4-RELEASE #1.

    David
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  • Next message: Donatas: "Re: multiple interfaces"

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