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Re: [libvirt] [PATCH 5/7] virnetdevbandwidth.c: Separate tc filter creation to a function



On 04/14/2015 12:59 PM, Michal Privoznik wrote:
> Not only this simplifies the code a bit, it prepares the
> environment for upcoming patches. The new
> virNetDevBandwidthManipulateFilter() function is capable of both
> removing a filter and adding a new one. At the same time! Yeah,
> this is not currently used anywhere but look at the next commit
> where you'll see it.
>
> Signed-off-by: Michal Privoznik <mprivozn redhat com>
> ---
>  src/util/virnetdevbandwidth.c | 142 +++++++++++++++++++++++++++++++-----------
>  1 file changed, 106 insertions(+), 36 deletions(-)
>
> diff --git a/src/util/virnetdevbandwidth.c b/src/util/virnetdevbandwidth.c
> index 943178b..c57c8c0 100644
> --- a/src/util/virnetdevbandwidth.c
> +++ b/src/util/virnetdevbandwidth.c
> @@ -43,6 +43,107 @@ virNetDevBandwidthFree(virNetDevBandwidthPtr def)
>      VIR_FREE(def);
>  }
>  
> +/**
> + * virNetDevBandwidthManipulateFilter:
> + * @ifname: interface to operate on
> + * @ifmac_ptr: MAC of the interface to create filter over
> + * @id: filter ID
> + * @class_id: where to place traffic
> + * @remove_old: whether to remove the filter
> + * @create_new: whether to create the filter
> + *
> + * TC filters are as crucial for traffic shaping as QDiscs. While
> + * QDisc acts like black boxes deciding which packets should be

s/QDisc acts/QDiscs act/

> + * held up and which should be sent immediately, it's filter who

s/filter who/the filter that/

> + * places a packet into the box. So, we may end up constructing a
> + * set of filters on a single device (e.g. a bridge) and filter
> + * the traffic into QDiscs based on the originating vNET device.
> + *
> + * Long story short, @ifname is the interface where the filter
> + * should be created. The @ifmac_ptr is the MAC address for which
> + * the filter should be created (usually different to the MAC
> + * address of @ifname). Then, like everything - even filters have
> + * an @id which should be unique (per @ifname). And @class_id
> + * tells into which QDisc should filter place the traffic.

I think this would be better as a bullet list of parameters with their
purposes, rather than a chummy paragraph of text :-)

> + *
> + * This function can be used for both, removing stale filter
> + * (@remove_old set to true) and creating new one (@create_new
> + * set to true). Both at once for the same price!

Same here. Not that I don't appreciate the nice tone of the
conversation, it's just easier to pick out what you need to know from a
list than from a paragraph.


> + *
> + * Returns: 0 on success,
> + *         -1 otherwise (with error reported).
> + */
> +static int ATTRIBUTE_NONNULL(1)
> +virNetDevBandwidthManipulateFilter(const char *ifname,
> +                                   const virMacAddr *ifmac_ptr,
> +                                   unsigned int id,
> +                                   const char *class_id,
> +                                   bool remove_old,
> +                                   bool create_new)

How about making these two flags so that it will be easier to tell
what's intended when looking at a call to the function?

> +{
> +    int ret = -1;
> +    char *filter_id = NULL;
> +    virCommandPtr cmd = NULL;
> +    unsigned char ifmac[VIR_MAC_BUFLEN];
> +    char *mac[2] = {NULL, NULL};
> +
> +    if (!(remove_old || create_new)) {
> +        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> +                       _("filter creation API error"));
> +        goto cleanup;
> +    }


I'm never sure how far to go with this type of checking on args that are
only given literal values in internal-only functions (especially
static). Especially if it's static and only called from one or two
places, I tend to go on the light side. Every new log message is one
more thing to translate, and one more bit of space taken up...


ACK, modulo the above comments (any of which you can take or leave) and
assuming your functional testing showed it to produce identical results
to previous behavior (which I'm guessing is true, since you've just
found another bug that would have been noticed by testing bandwidth
management while restarting libvirtd :-)

> +
> +    /* u32 filters must have 800:: prefix. Don't ask. */
> +    if (virAsprintf(&filter_id, "800::%u", id) < 0)
> +        goto cleanup;
> +
> +    if (remove_old) {
> +        int cmd_ret = 0;
> +
> +        cmd = virCommandNew(TC);
> +        virCommandAddArgList(cmd, "filter", "del", "dev", ifname,
> +                             "prio", "2", "handle",  filter_id, "u32", NULL);
> +
> +        if (virCommandRun(cmd, &cmd_ret) < 0)
> +            goto cleanup;
> +
> +    }
> +
> +    if (create_new) {
> +        virMacAddrGetRaw(ifmac_ptr, ifmac);
> +
> +        if (virAsprintf(&mac[0], "0x%02x%02x%02x%02x", ifmac[2],
> +                        ifmac[3], ifmac[4], ifmac[5]) < 0 ||
> +            virAsprintf(&mac[1], "0x%02x%02x", ifmac[0], ifmac[1]) < 0)
> +            goto cleanup;
> +
> +        virCommandFree(cmd);
> +        cmd = virCommandNew(TC);
> +        /* Okay, this not nice. But since libvirt does not necessarily track
> +         * interface IP address(es), and tc fw filter simply refuse to use
> +         * ebtables marks, we need to use u32 selector to match MAC address.
> +         * If libvirt will ever know something, remove this FIXME
> +         */
> +        virCommandAddArgList(cmd, "filter", "add", "dev", ifname, "protocol", "ip",
> +                             "prio", "2", "handle", filter_id, "u32",
> +                             "match", "u16", "0x0800", "0xffff", "at", "-2",
> +                             "match", "u32", mac[0], "0xffffffff", "at", "-12",
> +                             "match", "u16", mac[1], "0xffff", "at", "-14",
> +                             "flowid", class_id, NULL);
> +
> +        if (virCommandRun(cmd, NULL) < 0)
> +            goto cleanup;
> +    }
> +
> +    ret = 0;
> + cleanup:
> +    VIR_FREE(mac[1]);
> +    VIR_FREE(mac[0]);
> +    VIR_FREE(filter_id);
> +    virCommandFree(cmd);
> +    return ret;
> +}
> +
>  
>  /**
>   * virNetDevBandwidthSet:
> @@ -416,19 +517,15 @@ virNetDevBandwidthPlug(const char *brname,
>      virCommandPtr cmd = NULL;
>      char *class_id = NULL;
>      char *qdisc_id = NULL;
> -    char *filter_id = NULL;
>      char *floor = NULL;
>      char *ceil = NULL;
> -    unsigned char ifmac[VIR_MAC_BUFLEN];
>      char ifmacStr[VIR_MAC_STRING_BUFLEN];
> -    char *mac[2] = {NULL, NULL};
>  
>      if (id <= 2) {
>          virReportError(VIR_ERR_INTERNAL_ERROR, _("Invalid class ID %d"), id);
>          return -1;
>      }
>  
> -    virMacAddrGetRaw(ifmac_ptr, ifmac);
>      virMacAddrFormat(ifmac_ptr, ifmacStr);
>  
>      if (!net_bandwidth || !net_bandwidth->in) {
> @@ -441,10 +538,6 @@ virNetDevBandwidthPlug(const char *brname,
>  
>      if (virAsprintf(&class_id, "1:%x", id) < 0 ||
>          virAsprintf(&qdisc_id, "%x:", id) < 0 ||
> -        virAsprintf(&filter_id, "%u", id) < 0 ||
> -        virAsprintf(&mac[0], "0x%02x%02x%02x%02x", ifmac[2],
> -                    ifmac[3], ifmac[4], ifmac[5]) < 0 ||
> -        virAsprintf(&mac[1], "0x%02x%02x", ifmac[0], ifmac[1]) < 0 ||
>          virAsprintf(&floor, "%llukbps", bandwidth->in->floor) < 0 ||
>          virAsprintf(&ceil, "%llukbps", net_bandwidth->in->peak ?
>                      net_bandwidth->in->peak :
> @@ -468,31 +561,15 @@ virNetDevBandwidthPlug(const char *brname,
>      if (virCommandRun(cmd, NULL) < 0)
>          goto cleanup;
>  
> -    virCommandFree(cmd);
> -    cmd = virCommandNew(TC);
> -    /* Okay, this not nice. But since libvirt does not know anything about
> -     * interface IP address(es), and tc fw filter simply refuse to use ebtables
> -     * marks, we need to use u32 selector to match MAC address.
> -     * If libvirt will ever know something, remove this FIXME
> -     */
> -    virCommandAddArgList(cmd, "filter", "add", "dev", brname, "protocol", "ip",
> -                         "prio", filter_id, "u32",
> -                         "match", "u16", "0x0800", "0xffff", "at", "-2",
> -                         "match", "u32", mac[0], "0xffffffff", "at", "-12",
> -                         "match", "u16", mac[1], "0xffff", "at", "-14",
> -                         "flowid", class_id, NULL);
> -
> -    if (virCommandRun(cmd, NULL) < 0)
> +    if (virNetDevBandwidthManipulateFilter(brname, ifmac_ptr, id,
> +                                           class_id, false, true) < 0)
>          goto cleanup;
>  
>      ret = 0;
>  
>   cleanup:
> -    VIR_FREE(mac[1]);
> -    VIR_FREE(mac[0]);
>      VIR_FREE(ceil);
>      VIR_FREE(floor);
> -    VIR_FREE(filter_id);
>      VIR_FREE(qdisc_id);
>      VIR_FREE(class_id);
>      virCommandFree(cmd);
> @@ -517,7 +594,6 @@ virNetDevBandwidthUnplug(const char *brname,
>      virCommandPtr cmd = NULL;
>      char *class_id = NULL;
>      char *qdisc_id = NULL;
> -    char *filter_id = NULL;
>  
>      if (id <= 2) {
>          virReportError(VIR_ERR_INTERNAL_ERROR, _("Invalid class ID %d"), id);
> @@ -525,8 +601,7 @@ virNetDevBandwidthUnplug(const char *brname,
>      }
>  
>      if (virAsprintf(&class_id, "1:%x", id) < 0 ||
> -        virAsprintf(&qdisc_id, "%x:", id) < 0 ||
> -        virAsprintf(&filter_id, "%u", id) < 0)
> +        virAsprintf(&qdisc_id, "%x:", id) < 0)
>          goto cleanup;
>  
>      cmd = virCommandNew(TC);
> @@ -538,12 +613,8 @@ virNetDevBandwidthUnplug(const char *brname,
>      if (virCommandRun(cmd, &cmd_ret) < 0)
>          goto cleanup;
>  
> -    virCommandFree(cmd);
> -    cmd = virCommandNew(TC);
> -    virCommandAddArgList(cmd, "filter", "del", "dev", brname,
> -                         "prio", filter_id, NULL);
> -
> -    if (virCommandRun(cmd, &cmd_ret) < 0)
> +    if (virNetDevBandwidthManipulateFilter(brname, NULL, id,
> +                                           NULL, true, false) < 0)
>          goto cleanup;
>  
>      virCommandFree(cmd);
> @@ -557,7 +628,6 @@ virNetDevBandwidthUnplug(const char *brname,
>      ret = 0;
>  
>   cleanup:
> -    VIR_FREE(filter_id);
>      VIR_FREE(qdisc_id);
>      VIR_FREE(class_id);
>      virCommandFree(cmd);


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