diff mbox series

[net-next,v5,2/2] pktgen: Introducing 'SHARED' flag for testing with non-shared skb

Message ID 20230920125658.46978-2-liangchen.linux@gmail.com (mailing list archive)
State Accepted
Commit 7c7dd1d64910d07ab36b858d53d00e89b6d918d6
Delegated to: Netdev Maintainers
Headers show
Series [net-next,v5,1/2] pktgen: Automate flag enumeration for unknown flag handling | expand

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Context Check Description
netdev/series_format success Single patches do not need cover letters
netdev/tree_selection success Clearly marked for net-next
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 1340 this patch: 1340
netdev/cc_maintainers success CCed 13 of 13 maintainers
netdev/build_clang success Errors and warnings before: 1363 this patch: 1363
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 1363 this patch: 1363
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 185 lines checked
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

Liang Chen Sept. 20, 2023, 12:56 p.m. UTC 
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@gmail.com>
Reviewed-by: Benjamin Poirier <bpoirier@nvidia.com>
---
 Changes from v4:
- read the shared flag once in pktgen_xmit to avoid inconsistent burst,
  clone and shared flag values.
---
 Documentation/networking/pktgen.rst | 12 ++++++
 net/core/pktgen.c                   | 64 ++++++++++++++++++++++++-----
 2 files changed, 66 insertions(+), 10 deletions(-)
diff mbox series

Patch

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..5e865af82e5b 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;
@@ -3446,12 +3461,24 @@  static void pktgen_wait_for_skb(struct pktgen_dev *pkt_dev)
 
 static void pktgen_xmit(struct pktgen_dev *pkt_dev)
 {
-	unsigned int burst = READ_ONCE(pkt_dev->burst);
+	bool skb_shared = !!(READ_ONCE(pkt_dev->flags) & F_SHARED);
 	struct net_device *odev = pkt_dev->odev;
 	struct netdev_queue *txq;
+	unsigned int burst = 1;
 	struct sk_buff *skb;
+	int clone_skb = 0;
 	int ret;
 
+	/* If 'skb_shared' is false, the read of possible
+	 * new values (if any) for 'burst' and 'clone_skb' will be skipped to
+	 * prevent some concurrent changes from slipping in. And the stabilized
+	 * config will be read in during the next run of pktgen_xmit.
+	 */
+	if (skb_shared) {
+		burst = READ_ONCE(pkt_dev->burst);
+		clone_skb = READ_ONCE(pkt_dev->clone_skb);
+	}
+
 	/* If device is offline, then don't send */
 	if (unlikely(!netif_running(odev) || !netif_carrier_ok(odev))) {
 		pktgen_stop_device(pkt_dev);
@@ -3468,7 +3495,7 @@  static void pktgen_xmit(struct pktgen_dev *pkt_dev)
 
 	/* If no skb or clone count exhausted then get new one */
 	if (!pkt_dev->skb || (pkt_dev->last_ok &&
-			      ++pkt_dev->clone_count >= pkt_dev->clone_skb)) {
+			      ++pkt_dev->clone_count >= clone_skb)) {
 		/* build a new pkt */
 		kfree_skb(pkt_dev->skb);
 
@@ -3489,7 +3516,8 @@  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 (skb_shared)
+			refcount_add(burst, &skb->users);
 		local_bh_disable();
 		do {
 			ret = netif_receive_skb(skb);
@@ -3497,6 +3525,10 @@  static void pktgen_xmit(struct pktgen_dev *pkt_dev)
 				pkt_dev->errors++;
 			pkt_dev->sofar++;
 			pkt_dev->seq_num++;
+			if (unlikely(!skb_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 +3547,14 @@  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 (skb_shared)
+			refcount_inc(&pkt_dev->skb->users);
 
 		ret = dev_queue_xmit(pkt_dev->skb);
+
+		if (!skb_shared && dev_xmit_complete(ret))
+			pkt_dev->skb = NULL;
+
 		switch (ret) {
 		case NET_XMIT_SUCCESS:
 			pkt_dev->sofar++;
@@ -3555,11 +3592,15 @@  static void pktgen_xmit(struct pktgen_dev *pkt_dev)
 		pkt_dev->last_ok = 0;
 		goto unlock;
 	}
-	refcount_add(burst, &pkt_dev->skb->users);
+	if (skb_shared)
+		refcount_add(burst, &pkt_dev->skb->users);
 
 xmit_more:
 	ret = netdev_start_xmit(pkt_dev->skb, odev, txq, --burst > 0);
 
+	if (!skb_shared && dev_xmit_complete(ret))
+		pkt_dev->skb = NULL;
+
 	switch (ret) {
 	case NETDEV_TX_OK:
 		pkt_dev->last_ok = 1;
@@ -3581,7 +3622,8 @@  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 (skb_shared)
+			refcount_dec(&pkt_dev->skb->users);
 		pkt_dev->last_ok = 0;
 	}
 	if (unlikely(burst))
@@ -3594,7 +3636,8 @@  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 +3820,7 @@  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)