net: remove skb_orphan_try()

Orphaning skb in dev_hard_start_xmit() makes bonding behavior
unfriendly for applications sending big UDP bursts : Once packets
pass the bonding device and come to real device, they might hit a full
qdisc and be dropped. Without orphaning, the sender is automatically
throttled because sk->sk_wmemalloc reaches sk->sk_sndbuf (assuming
sk_sndbuf is not too big)

We could try to defer the orphaning adding another test in
dev_hard_start_xmit(), but all this seems of little gain,
now that BQL tends to make packets more likely to be parked
in Qdisc queues instead of NIC TX ring, in cases where performance
matters.

Reverts commits :
fc6055a5ba31 net: Introduce skb_orphan_try()
87fd308cfc6b net: skb_tx_hash() fix relative to skb_orphan_try()
and removes SKBTX_DRV_NEEDS_SK_REF flag

Reported-and-bisected-by: Jean-Michel Hautbois <[e-mail]>
Signed-off-by: Eric Dumazet <[e-mail]>
Tested-by: Oliver Hartkopp <[e-mail]>
Acked-by: Oliver Hartkopp <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/linux/skbuff.h

···
 	/* device driver is going to provide hardware time stamp */
 	SKBTX_IN_PROGRESS = 1 << 2,
 
-	/* ensure the originating sk reference is available on driver level */
-	SKBTX_DRV_NEEDS_SK_REF = 1 << 3,
-
 	/* device driver supports TX zero-copy buffers */
-	SKBTX_DEV_ZEROCOPY = 1 << 4,
+	SKBTX_DEV_ZEROCOPY = 1 << 3,
 
 	/* generate wifi status information (where possible) */
-	SKBTX_WIFI_STATUS = 1 << 5,
+	SKBTX_WIFI_STATUS = 1 << 4,
 };
 
 /*

net/can/raw.c

···
 	if (err < 0)
 		goto free_skb;
 
-	/* to be able to check the received tx sock reference in raw_rcv() */
-	skb_shinfo(skb)->tx_flags |= SKBTX_DRV_NEEDS_SK_REF;
-
 	skb->dev = dev;
 	skb->sk  = sk;
 

net/core/dev.c

···
 	return 0;
 }
 
-/*
- * Try to orphan skb early, right before transmission by the device.
- * We cannot orphan skb if tx timestamp is requested or the sk-reference
- * is needed on driver level for other reasons, e.g. see net/can/raw.c
- */
-static inline void skb_orphan_try(struct sk_buff *skb)
-{
-	struct sock *sk = skb->sk;
-
-	if (sk && !skb_shinfo(skb)->tx_flags) {
-		/* skb_tx_hash() wont be able to get sk.
-		 * We copy sk_hash into skb->rxhash
-		 */
-		if (!skb->rxhash)
-			skb->rxhash = sk->sk_hash;
-		skb_orphan(skb);
-	}
-}
-
 static bool can_checksum_protocol(netdev_features_t features, __be16 protocol)
 {
 	return ((features & NETIF_F_GEN_CSUM) ||
···
 
 		if (!list_empty(&ptype_all))
 			dev_queue_xmit_nit(skb, dev);
-
-		skb_orphan_try(skb);
 
 		features = netif_skb_features(skb);
 
···
 	if (skb->sk && skb->sk->sk_hash)
 		hash = skb->sk->sk_hash;
 	else
-		hash = (__force u16) skb->protocol ^ skb->rxhash;
+		hash = (__force u16) skb->protocol;
 	hash = jhash_1word(hash, hashrnd);
 
 	return (u16) (((u64) hash * qcount) >> 32) + qoffset;

net/iucv/af_iucv.c

···
 			skb_trim(skb, skb->dev->mtu);
 	}
 	skb->protocol = ETH_P_AF_IUCV;
-	skb_shinfo(skb)->tx_flags |= SKBTX_DRV_NEEDS_SK_REF;
 	nskb = skb_clone(skb, GFP_ATOMIC);
 	if (!nskb)
 		return -ENOMEM;