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Date: Wed, 20 Sep 2023 12:00:50 +0800
From: Liang Chen <liangchen.linux@...il.com>
To: Benjamin Poirier <bpoirier@...dia.com>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
pabeni@...hat.com, netdev@...r.kernel.org, Jonathan Corbet <corbet@....net>,
"Jason A. Donenfeld" <Jason@...c4.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Kees Cook <keescook@...omium.org>, "Darrick J. Wong" <djwong@...nel.org>,
Yunsheng Lin <linyunsheng@...wei.com>, linux-doc@...r.kernel.org
Subject: Re: [PATCH net-next v4 2/2] pktgen: Introducing 'SHARED' flag for
testing with non-shared skb
On Mon, Sep 18, 2023 at 10:22 PM Benjamin Poirier <bpoirier@...dia.com> wrote:
>
> On 2023-09-16 21:29 +0800, Liang Chen wrote:
> > Currently, skbs generated by pktgen always have their reference count
> > incremented before transmission, causing their reference count to be
> > always greater than 1, leading to two issues:
> > 1. Only the code paths for shared skbs can be tested.
> > 2. In certain situations, skbs can only be released by pktgen.
> > To enhance testing comprehensiveness, we are introducing the "SHARED"
> > flag to indicate whether an SKB is shared. This flag is enabled by
> > default, aligning with the current behavior. However, disabling this
> > flag allows skbs with a reference count of 1 to be transmitted.
> > So we can test non-shared skbs and code paths where skbs are released
> > within the stack.
> >
> > Signed-off-by: Liang Chen <liangchen.linux@...il.com>
> > ---
>
> In the future, please run scripts/get_maintainer.pl and cc the listed
> addresses. I'm adding them now.
Sure. Thanks!
>
> Reviewed-by: Benjamin Poirier <bpoirier@...dia.com>
>
> > Documentation/networking/pktgen.rst | 12 ++++++++
> > net/core/pktgen.c | 48 ++++++++++++++++++++++++-----
> > 2 files changed, 52 insertions(+), 8 deletions(-)
> >
> > diff --git a/Documentation/networking/pktgen.rst b/Documentation/networking/pktgen.rst
> > index 1225f0f63ff0..c945218946e1 100644
> > --- a/Documentation/networking/pktgen.rst
> > +++ b/Documentation/networking/pktgen.rst
> > @@ -178,6 +178,7 @@ Examples::
> > IPSEC # IPsec encapsulation (needs CONFIG_XFRM)
> > NODE_ALLOC # node specific memory allocation
> > NO_TIMESTAMP # disable timestamping
> > + SHARED # enable shared SKB
> > pgset 'flag ![name]' Clear a flag to determine behaviour.
> > Note that you might need to use single quote in
> > interactive mode, so that your shell wouldn't expand
> > @@ -288,6 +289,16 @@ To avoid breaking existing testbed scripts for using AH type and tunnel mode,
> > you can use "pgset spi SPI_VALUE" to specify which transformation mode
> > to employ.
> >
> > +Disable shared SKB
> > +==================
> > +By default, SKBs sent by pktgen are shared (user count > 1).
> > +To test with non-shared SKBs, remove the "SHARED" flag by simply setting::
> > +
> > + pg_set "flag !SHARED"
> > +
> > +However, if the "clone_skb" or "burst" parameters are configured, the skb
> > +still needs to be held by pktgen for further access. Hence the skb must be
> > +shared.
> >
> > Current commands and configuration options
> > ==========================================
> > @@ -357,6 +368,7 @@ Current commands and configuration options
> > IPSEC
> > NODE_ALLOC
> > NO_TIMESTAMP
> > + SHARED
> >
> > spi (ipsec)
> >
> > diff --git a/net/core/pktgen.c b/net/core/pktgen.c
> > index 48306a101fd9..c4e0814df325 100644
> > --- a/net/core/pktgen.c
> > +++ b/net/core/pktgen.c
> > @@ -200,6 +200,7 @@
> > pf(VID_RND) /* Random VLAN ID */ \
> > pf(SVID_RND) /* Random SVLAN ID */ \
> > pf(NODE) /* Node memory alloc*/ \
> > + pf(SHARED) /* Shared SKB */ \
> >
> > #define pf(flag) flag##_SHIFT,
> > enum pkt_flags {
> > @@ -1198,7 +1199,8 @@ static ssize_t pktgen_if_write(struct file *file,
> > ((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)
> > + if (value > 0 && (pkt_dev->n_imix_entries > 0 ||
> > + !(pkt_dev->flags & F_SHARED)))
> > return -EINVAL;
> >
> > i += len;
> > @@ -1257,6 +1259,10 @@ static ssize_t pktgen_if_write(struct file *file,
> > ((pkt_dev->xmit_mode == M_START_XMIT) &&
> > (!(pkt_dev->odev->priv_flags & IFF_TX_SKB_SHARING)))))
> > return -ENOTSUPP;
> > +
> > + if (value > 1 && !(pkt_dev->flags & F_SHARED))
> > + return -EINVAL;
> > +
> > pkt_dev->burst = value < 1 ? 1 : value;
> > sprintf(pg_result, "OK: burst=%u", pkt_dev->burst);
> > return count;
> > @@ -1334,10 +1340,19 @@ static ssize_t pktgen_if_write(struct file *file,
> >
> > flag = pktgen_read_flag(f, &disable);
> > if (flag) {
> > - if (disable)
> > + if (disable) {
> > + /* If "clone_skb", or "burst" parameters are
> > + * configured, it means that the skb still
> > + * needs to be referenced by the pktgen, so
> > + * the skb must be shared.
> > + */
> > + if (flag == F_SHARED && (pkt_dev->clone_skb ||
> > + pkt_dev->burst > 1))
> > + return -EINVAL;
> > pkt_dev->flags &= ~flag;
> > - else
> > + } else {
> > pkt_dev->flags |= flag;
> > + }
> >
> > sprintf(pg_result, "OK: flags=0x%x", pkt_dev->flags);
> > return count;
> > @@ -3489,7 +3504,8 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev)
> > if (pkt_dev->xmit_mode == M_NETIF_RECEIVE) {
> > skb = pkt_dev->skb;
> > skb->protocol = eth_type_trans(skb, skb->dev);
> > - refcount_add(burst, &skb->users);
> > + if (pkt_dev->flags & F_SHARED)
> > + refcount_add(burst, &skb->users);
> > local_bh_disable();
> > do {
> > ret = netif_receive_skb(skb);
> > @@ -3497,6 +3513,10 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev)
> > pkt_dev->errors++;
> > pkt_dev->sofar++;
> > pkt_dev->seq_num++;
> > + if (unlikely(!(pkt_dev->flags & F_SHARED))) {
> > + pkt_dev->skb = NULL;
> > + break;
> > + }
> > if (refcount_read(&skb->users) != burst) {
> > /* skb was queued by rps/rfs or taps,
> > * so cannot reuse this skb
> > @@ -3515,9 +3535,14 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev)
> > goto out; /* Skips xmit_mode M_START_XMIT */
> > } else if (pkt_dev->xmit_mode == M_QUEUE_XMIT) {
> > local_bh_disable();
> > - refcount_inc(&pkt_dev->skb->users);
> > + if (pkt_dev->flags & F_SHARED)
> > + refcount_inc(&pkt_dev->skb->users);
> >
> > ret = dev_queue_xmit(pkt_dev->skb);
> > +
> > + if (!(pkt_dev->flags & F_SHARED) && dev_xmit_complete(ret))
> > + pkt_dev->skb = NULL;
> > +
> > switch (ret) {
> > case NET_XMIT_SUCCESS:
> > pkt_dev->sofar++;
> > @@ -3555,11 +3580,15 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev)
> > pkt_dev->last_ok = 0;
> > goto unlock;
> > }
> > - refcount_add(burst, &pkt_dev->skb->users);
> > + if (pkt_dev->flags & F_SHARED)
> > + refcount_add(burst, &pkt_dev->skb->users);
> >
> > xmit_more:
> > ret = netdev_start_xmit(pkt_dev->skb, odev, txq, --burst > 0);
> >
> > + if (!(pkt_dev->flags & F_SHARED) && dev_xmit_complete(ret))
> > + pkt_dev->skb = NULL;
> > +
> > switch (ret) {
> > case NETDEV_TX_OK:
> > pkt_dev->last_ok = 1;
> > @@ -3581,7 +3610,8 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev)
> > fallthrough;
> > case NETDEV_TX_BUSY:
> > /* Retry it next time */
> > - refcount_dec(&(pkt_dev->skb->users));
> > + if (pkt_dev->flags & F_SHARED)
> > + refcount_dec(&pkt_dev->skb->users);
> > pkt_dev->last_ok = 0;
> > }
> > if (unlikely(burst))
> > @@ -3594,7 +3624,8 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev)
> >
> > /* If pkt_dev->count is zero, then run forever */
> > if ((pkt_dev->count != 0) && (pkt_dev->sofar >= pkt_dev->count)) {
> > - pktgen_wait_for_skb(pkt_dev);
> > + if (pkt_dev->skb)
> > + pktgen_wait_for_skb(pkt_dev);
> >
> > /* Done with this */
> > pktgen_stop_device(pkt_dev);
> > @@ -3777,6 +3808,7 @@ static int pktgen_add_device(struct pktgen_thread *t, const char *ifname)
> > pkt_dev->svlan_id = 0xffff;
> > pkt_dev->burst = 1;
> > pkt_dev->node = NUMA_NO_NODE;
> > + pkt_dev->flags = F_SHARED; /* SKB shared by default */
> >
> > err = pktgen_setup_dev(t->net, pkt_dev, ifname);
> > if (err)
> > --
> > 2.40.1
> >
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