Re: [PATCH 1/3] pktgen: Parse internet mix (imix) input

[Nick Richardson <richardsonnick@google.com>]

Hey Jakub, thanks for the quick response!

> > +
> > +             len = num_arg(&buffer[i], max_digits, &size);
> > +             if (len < 0)
> > +                     return len;
> > +             i += len;
> > +             if (get_user(c, &buffer[i]))
> > +                     return -EFAULT;
> > +             /* Check for comma between size_i and weight_i */
> > +             if (c != ',')
> > +                     return -EINVAL;
> > +             i++;
> > +
> > +             if (size < 14 + 20 + 8)
> > +                     size = 14 + 20 + 8;
>
> Why overwrite instead of rejecting?

I overwrite here to keep behavior similar to when pkt_size is set directly.
When the pkt_size command is used the size value is overwritten to the
minimum packet size (14 + 8 + 20).
See the pkt_size section in pktgen_if_write().

>
> > +             len = num_arg(&buffer[i], max_digits, &weight);
> > +             if (len < 0)
> > +                     return len;
> > +             if (weight <= 0)
> > +                     return -EINVAL;
> > +
> > +             pkt_dev->imix_entries[pkt_dev->n_imix_entries].size = size;
> > +             pkt_dev->imix_entries[pkt_dev->n_imix_entries].weight = weight;
> > +
> > +             i += len;
> > +             if (get_user(c, &buffer[i]))
> > +                     return -EFAULT;
>
> What if this is the last entry?

If this is the last entry then the line terminating character is read.
Similar code can be found in the get_labels() function in pktgen.c


On Mon, Aug 9, 2021 at 5:05 PM Jakub Kicinski <kuba@kernel.org> wrote:
>
> On Mon,  9 Aug 2021 17:22:02 +0000 Nicholas Richardson wrote:
> > From: Nick Richardson <richardsonnick@google.com>
> >
> > Adds "imix_weights" command for specifying internet mix distribution.
> >
> > The command is in this format:
> > "imix_weights size_1,weight_1 size_2,weight_2 ... size_n,weight_n"
> > where the probability that packet size_i is picked is:
> > weight_i / (weight_1 + weight_2 + .. + weight_n)
> >
> > The user may provide up to 20 imix entries (size_i,weight_i) in this
> > command.
> >
> > The user specified imix entries will be displayed in the "Params"
> > section of the interface output.
> >
> > Values for clone_skb > 0 is not supported in IMIX mode.
> >
> > Summary of changes:
> > Add flag for enabling internet mix mode.
> > Add command (imix_weights) for internet mix input.
> > Return -ENOTSUPP when clone_skb > 0 in IMIX mode.
> > Display imix_weights in Params.
> > Create data structures to store imix entries and distribution.
> >
> > Signed-off-by: Nick Richardson <richardsonnick@google.com>
> > ---
> >  net/core/pktgen.c | 95 +++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 95 insertions(+)
> >
> > diff --git a/net/core/pktgen.c b/net/core/pktgen.c
> > index 7e258d255e90..83c83e1b5f28 100644
> > --- a/net/core/pktgen.c
> > +++ b/net/core/pktgen.c
> > @@ -175,6 +175,8 @@
> >  #define IP_NAME_SZ 32
> >  #define MAX_MPLS_LABELS 16 /* This is the max label stack depth */
> >  #define MPLS_STACK_BOTTOM htonl(0x00000100)
> > +/* Max number of internet mix entries that can be specified in imix_weights. */
> > +#define MAX_IMIX_ENTRIES 20
> >
> >  #define func_enter() pr_debug("entering %s\n", __func__);
> >
> > @@ -242,6 +244,12 @@ static char *pkt_flag_names[] = {
> >  #define VLAN_TAG_SIZE(x) ((x)->vlan_id == 0xffff ? 0 : 4)
> >  #define SVLAN_TAG_SIZE(x) ((x)->svlan_id == 0xffff ? 0 : 4)
> >
> > +struct imix_pkt {
> > +     __u64 size;
> > +     __u64 weight;
> > +     __u64 count_so_far;
>
> no need for the __ prefix outside of uAPI.
>
> > +};
> > +
> >  struct flow_state {
> >       __be32 cur_daddr;
> >       int count;
> > @@ -343,6 +351,10 @@ struct pktgen_dev {
> >       __u8 traffic_class;  /* ditto for the (former) Traffic Class in IPv6
> >                               (see RFC 3260, sec. 4) */
> >
> > +     /* IMIX */
> > +     unsigned int n_imix_entries;
> > +     struct imix_pkt imix_entries[MAX_IMIX_ENTRIES];
> > +
> >       /* MPLS */
> >       unsigned int nr_labels; /* Depth of stack, 0 = no MPLS */
> >       __be32 labels[MAX_MPLS_LABELS];
> > @@ -552,6 +564,16 @@ static int pktgen_if_show(struct seq_file *seq, void *v)
> >                  (unsigned long long)pkt_dev->count, pkt_dev->min_pkt_size,
> >                  pkt_dev->max_pkt_size);
> >
> > +     if (pkt_dev->n_imix_entries > 0) {
> > +             seq_printf(seq, "     imix_weights: ");
> > +             for (i = 0; i < pkt_dev->n_imix_entries; i++) {
> > +                     seq_printf(seq, "%llu,%llu ",
> > +                                pkt_dev->imix_entries[i].size,
> > +                                pkt_dev->imix_entries[i].weight);
> > +             }
> > +             seq_printf(seq, "\n");
>
> seq_puts()
>
> > +     }
> > +
> >       seq_printf(seq,
> >                  "     frags: %d  delay: %llu  clone_skb: %d  ifname: %s\n",
> >                  pkt_dev->nfrags, (unsigned long long) pkt_dev->delay,
> > @@ -792,6 +814,61 @@ static int strn_len(const char __user * user_buffer, unsigned int maxlen)
> >       return i;
> >  }
> >
> > +static ssize_t get_imix_entries(const char __user *buffer,
> > +                             struct pktgen_dev *pkt_dev)
> > +{
> > +     /* Parses imix entries from user buffer.
> > +      * The user buffer should consist of imix entries separated by spaces
> > +      * where each entry consists of size and weight delimited by commas.
> > +      * "size1,weight_1 size2,weight_2 ... size_n,weight_n" for example.
> > +      */
>
> This comments belongs before the function.
>
> > +     long len;
> > +     char c;
> > +     int i = 0;
> > +     const int max_digits = 10;
>
> Please order these lines longest to shortest (reverse xmas tree).
>
> > +     pkt_dev->n_imix_entries = 0;
> > +
> > +     do {
> > +             unsigned long size;
> > +             unsigned long weight;
>
> same
>
> > +
> > +             len = num_arg(&buffer[i], max_digits, &size);
> > +             if (len < 0)
> > +                     return len;
> > +             i += len;
> > +             if (get_user(c, &buffer[i]))
> > +                     return -EFAULT;
> > +             /* Check for comma between size_i and weight_i */
> > +             if (c != ',')
> > +                     return -EINVAL;
> > +             i++;
> > +
> > +             if (size < 14 + 20 + 8)
> > +                     size = 14 + 20 + 8;
>
> Why overwrite instead of rejecting?
>
> > +             len = num_arg(&buffer[i], max_digits, &weight);
> > +             if (len < 0)
> > +                     return len;
> > +             if (weight <= 0)
> > +                     return -EINVAL;
> > +
> > +             pkt_dev->imix_entries[pkt_dev->n_imix_entries].size = size;
> > +             pkt_dev->imix_entries[pkt_dev->n_imix_entries].weight = weight;
> > +
> > +             i += len;
> > +             if (get_user(c, &buffer[i]))
> > +                     return -EFAULT;
>
> What if this is the last entry?
>
> > +             i++;
> > +             pkt_dev->n_imix_entries++;
> > +
> > +             if (pkt_dev->n_imix_entries > MAX_IMIX_ENTRIES)
> > +                     return -E2BIG;
> > +     } while (c == ' ');
>
> empty line here
>
> > +     return i;
> > +}
> > +
> >  static ssize_t get_labels(const char __user *buffer, struct pktgen_dev *pkt_dev)
> >  {
> >       unsigned int n = 0;
> > @@ -960,6 +1037,18 @@ static ssize_t pktgen_if_write(struct file *file,
> >               return count;
> >       }
> >
> > +     if (!strcmp(name, "imix_weights")) {
> > +             if (pkt_dev->clone_skb > 0)
> > +                     return -ENOTSUPP;
>
> ENOTSUPP should not be returned to user space, please use a different
> one.
>
> > +             len = get_imix_entries(&user_buffer[i], pkt_dev);
> > +             if (len < 0)
> > +                     return len;
> > +
> > +             i += len;
> > +             return count;
> > +     }
> > +
> >       if (!strcmp(name, "debug")) {
> >               len = num_arg(&user_buffer[i], 10, &value);
> >               if (len < 0)
> > @@ -1082,10 +1171,16 @@ static ssize_t pktgen_if_write(struct file *file,
> >               len = num_arg(&user_buffer[i], 10, &value);
> >               if (len < 0)
> >                       return len;
> > +             /* clone_skb is not supported for netif_receive xmit_mode and
> > +              * IMIX mode.
> > +              */
> >               if ((value > 0) &&
> >                   ((pkt_dev->xmit_mode == M_NETIF_RECEIVE) ||
> >                    !(pkt_dev->odev->priv_flags & IFF_TX_SKB_SHARING)))
> >                       return -ENOTSUPP;
> > +             if (value > 0 && pkt_dev->n_imix_entries > 0)
> > +                     return -ENOTSUPP;
>
> ditto
>
> >               i += len;
> >               pkt_dev->clone_skb = value;
> >
>


-- 





Nick Richardson (he/him/his)

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