Merge branch 'csums-next'

Tom Herbert says:

====================
net: Checksum offload changes - Part VI

I am working on overhauling RX checksum offload. Goals of this effort
are:

- Specify what exactly it means when driver returns CHECKSUM_UNNECESSARY
- Preserve CHECKSUM_COMPLETE through encapsulation layers
- Don't do skb_checksum more than once per packet
- Unify GRO and non-GRO csum verification as much as possible
- Unify the checksum functions (checksum_init)
- Simplify code

What is in this sixth patch set:

- Clarify the specific requirements of devices returning
  CHECKSUM_UNNECESSARY (comments in skbuff.h).
- Add csum_level field to skbuff. This is used to express how
  many checksums are covered by CHECKSUM_UNNECESSARY (stores n - 1).
- Change __skb_checksum_validate_needed to "consume" each checksum
  as indicated by csum_level as layers of the the packet are parsed.
- Remove skb_pop_rcv_encapsulation, no longer needed in the new
  csum_level model.
- Allow GRO path to "consume" checksums provided in CHECKSUM_UNNECESSARY
  and to report new verfied checksums for use in normal path fallback.
- Add proper support to SCTP to accept CHECKSUM_UNNECESSARY to validate
  header CRC.
- Modify drivers to set skb->csum_level instead of setting
  skb->encapsulation to indicate validation of an encapsulated
  checksum on receive.

v2:

Allocate a new 16 bits for flags in skbuff.

Please review carefully and test if possible, mucking with basic
checksum functions is always a little precarious :-)
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/emulex/benet/be_main.c

@@ -1683,7 +1683,7 @@ static void be_rx_compl_process(struct be_rx_obj *rxo, struct napi_struct *napi,
 	if (netdev->features & NETIF_F_RXHASH)
 		skb_set_hash(skb, rxcp->rss_hash, PKT_HASH_TYPE_L3);
 
-	skb->encapsulation = rxcp->tunneled;
+	skb->csum_level = rxcp->tunneled;
 	skb_mark_napi_id(skb, napi);
 
 	if (rxcp->vlanf)
@@ -1741,7 +1741,7 @@ static void be_rx_compl_process_gro(struct be_rx_obj *rxo,
 	if (adapter->netdev->features & NETIF_F_RXHASH)
 		skb_set_hash(skb, rxcp->rss_hash, PKT_HASH_TYPE_L3);
 
-	skb->encapsulation = rxcp->tunneled;
+	skb->csum_level = rxcp->tunneled;
 	skb_mark_napi_id(skb, napi);
 
 	if (rxcp->vlanf)

drivers/net/ethernet/intel/i40e/i40e_txrx.c

@@ -1241,7 +1241,6 @@ static inline void i40e_rx_checksum(struct i40e_vsi *vsi,
 	ipv6_tunnel = (rx_ptype > I40E_RX_PTYPE_GRENAT6_MAC_PAY3) &&
 		      (rx_ptype < I40E_RX_PTYPE_GRENAT6_MACVLAN_IPV6_ICMP_PAY4);
 
-	skb->encapsulation = ipv4_tunnel || ipv6_tunnel;
 	skb->ip_summed = CHECKSUM_NONE;
 
 	/* Rx csum enabled and ip headers found? */
@@ -1315,6 +1314,7 @@ static inline void i40e_rx_checksum(struct i40e_vsi *vsi,
 	}
 
 	skb->ip_summed = CHECKSUM_UNNECESSARY;
+	skb->csum_level = ipv4_tunnel || ipv6_tunnel;
 
 	return;
 

drivers/net/ethernet/intel/i40evf/i40e_txrx.c

@@ -746,7 +746,6 @@ static inline void i40e_rx_checksum(struct i40e_vsi *vsi,
 	ipv6_tunnel = (rx_ptype > I40E_RX_PTYPE_GRENAT6_MAC_PAY3) &&
 		      (rx_ptype < I40E_RX_PTYPE_GRENAT6_MACVLAN_IPV6_ICMP_PAY4);
 
-	skb->encapsulation = ipv4_tunnel || ipv6_tunnel;
 	skb->ip_summed = CHECKSUM_NONE;
 
 	/* Rx csum enabled and ip headers found? */
@@ -820,6 +819,7 @@ static inline void i40e_rx_checksum(struct i40e_vsi *vsi,
 	}
 
 	skb->ip_summed = CHECKSUM_UNNECESSARY;
+	skb->csum_level = ipv4_tunnel || ipv6_tunnel;
 
 	return;
 

drivers/net/ethernet/mellanox/mlx4/en_rx.c

@@ -769,7 +769,7 @@ int mlx4_en_process_rx_cq(struct net_device *dev, struct mlx4_en_cq *cq, int bud
 					gro_skb->ip_summed = CHECKSUM_UNNECESSARY;
 
 					if (l2_tunnel)
-						gro_skb->encapsulation = 1;
+						gro_skb->csum_level = 1;
 					if ((cqe->vlan_my_qpn &
 					    cpu_to_be32(MLX4_CQE_VLAN_PRESENT_MASK)) &&
 					    (dev->features & NETIF_F_HW_VLAN_CTAG_RX)) {
@@ -823,8 +823,8 @@ int mlx4_en_process_rx_cq(struct net_device *dev, struct mlx4_en_cq *cq, int bud
 		skb->protocol = eth_type_trans(skb, dev);
 		skb_record_rx_queue(skb, cq->ring);
 
-		if (l2_tunnel)
-			skb->encapsulation = 1;
+		if (l2_tunnel && ip_summed == CHECKSUM_UNNECESSARY)
+			skb->csum_level = 1;
 
 		if (dev->features & NETIF_F_RXHASH)
 			skb_set_hash(skb,

drivers/net/ethernet/qlogic/qlcnic/qlcnic_io.c

@@ -1753,7 +1753,7 @@ qlcnic_83xx_process_rcv(struct qlcnic_adapter *adapter,
 
 	if (qlcnic_encap_length(sts_data[1]) &&
 	    skb->ip_summed == CHECKSUM_UNNECESSARY) {
-		skb->encapsulation = 1;
+		skb->csum_level = 1;
 		adapter->stats.encap_rx_csummed++;
 	}
 

drivers/net/vxlan.c

@@ -1158,8 +1158,6 @@ static int vxlan_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
 	if (!vs)
 		goto drop;
 
-	skb_pop_rcv_encapsulation(skb);
-
 	vs->rcv(vs, skb, vxh->vx_vni);
 	return 0;
 

include/linux/netdevice.h

@@ -1883,8 +1883,8 @@ struct napi_gro_cb {
 	/* GRO checksum is valid */
 	u8	csum_valid:1;
 
-	/* Number encapsulation layers crossed */
-	u8	encapsulation;
+	/* Number of checksums via CHECKSUM_UNNECESSARY */
+	u8	csum_cnt:3;
 
 	/* used to support CHECKSUM_COMPLETE for tunneling protocols */
 	__wsum	csum;
@@ -2179,8 +2179,7 @@ static inline bool __skb_gro_checksum_validate_needed(struct sk_buff *skb,
 						      __sum16 check)
 {
 	return (skb->ip_summed != CHECKSUM_PARTIAL &&
-		(skb->ip_summed != CHECKSUM_UNNECESSARY ||
-		 (NAPI_GRO_CB(skb)->encapsulation > skb->encapsulation)) &&
+		NAPI_GRO_CB(skb)->csum_cnt == 0 &&
 		(!zero_okay || check));
 }
 
@@ -2196,18 +2195,17 @@ static inline __sum16 __skb_gro_checksum_validate_complete(struct sk_buff *skb,
 	return __skb_gro_checksum_complete(skb);
 }
 
-/* Update skb for CHECKSUM_UNNECESSARY when we verified a top level
- * checksum or an encapsulated one during GRO. This saves work
- * if we fallback to normal path with the packet.
- */
 static inline void skb_gro_incr_csum_unnecessary(struct sk_buff *skb)
 {
-	if (skb->ip_summed == CHECKSUM_UNNECESSARY) {
-		if (NAPI_GRO_CB(skb)->encapsulation)
-			skb->encapsulation = 1;
-	} else if (skb->ip_summed != CHECKSUM_PARTIAL) {
-		skb->ip_summed = CHECKSUM_UNNECESSARY;
-		skb->encapsulation = 0;
+	if (NAPI_GRO_CB(skb)->csum_cnt > 0) {
+		/* Consume a checksum from CHECKSUM_UNNECESSARY */
+		NAPI_GRO_CB(skb)->csum_cnt--;
+	} else {
+		/* Update skb for CHECKSUM_UNNECESSARY and csum_level when we
+		 * verified a new top level checksum or an encapsulated one
+		 * during GRO. This saves work if we fallback to normal path.
+		 */
+		__skb_incr_checksum_unnecessary(skb);
 	}
 }
 

include/linux/skbuff.h

@@ -47,11 +47,29 @@
  *
  *   The hardware you're dealing with doesn't calculate the full checksum
  *   (as in CHECKSUM_COMPLETE), but it does parse headers and verify checksums
- *   for specific protocols e.g. TCP/UDP/SCTP, then, for such packets it will
- *   set CHECKSUM_UNNECESSARY if their checksums are okay. skb->csum is still
- *   undefined in this case though. It is a bad option, but, unfortunately,
- *   nowadays most vendors do this. Apparently with the secret goal to sell
- *   you new devices, when you will add new protocol to your host, f.e. IPv6 8)
+ *   for specific protocols. For such packets it will set CHECKSUM_UNNECESSARY
+ *   if their checksums are okay. skb->csum is still undefined in this case
+ *   though. It is a bad option, but, unfortunately, nowadays most vendors do
+ *   this. Apparently with the secret goal to sell you new devices, when you
+ *   will add new protocol to your host, f.e. IPv6 8)
+ *
+ *   CHECKSUM_UNNECESSARY is applicable to following protocols:
+ *     TCP: IPv6 and IPv4.
+ *     UDP: IPv4 and IPv6. A device may apply CHECKSUM_UNNECESSARY to a
+ *       zero UDP checksum for either IPv4 or IPv6, the networking stack
+ *       may perform further validation in this case.
+ *     GRE: only if the checksum is present in the header.
+ *     SCTP: indicates the CRC in SCTP header has been validated.
+ *
+ *   skb->csum_level indicates the number of consecutive checksums found in
+ *   the packet minus one that have been verified as CHECKSUM_UNNECESSARY.
+ *   For instance if a device receives an IPv6->UDP->GRE->IPv4->TCP packet
+ *   and a device is able to verify the checksums for UDP (possibly zero),
+ *   GRE (checksum flag is set), and TCP-- skb->csum_level would be set to
+ *   two. If the device were only able to verify the UDP checksum and not
+ *   GRE, either because it doesn't support GRE checksum of because GRE
+ *   checksum is bad, skb->csum_level would be set to zero (TCP checksum is
+ *   not considered in this case).
  *
  * CHECKSUM_COMPLETE:
  *
@@ -112,6 +130,9 @@
 #define CHECKSUM_COMPLETE	2
 #define CHECKSUM_PARTIAL	3
 
+/* Maximum value in skb->csum_level */
+#define SKB_MAX_CSUM_LEVEL	3
+
 #define SKB_DATA_ALIGN(X)	ALIGN(X, SMP_CACHE_BYTES)
 #define SKB_WITH_OVERHEAD(X)	\
 	((X) - SKB_DATA_ALIGN(sizeof(struct skb_shared_info)))
@@ -571,11 +592,7 @@ struct sk_buff {
 	__u8			wifi_acked:1;
 	__u8			no_fcs:1;
 	__u8			head_frag:1;
-	/* Encapsulation protocol and NIC drivers should use
-	 * this flag to indicate to each other if the skb contains
-	 * encapsulated packet or not and maybe use the inner packet
-	 * headers if needed
-	 */
+	/* Indicates the inner headers are valid in the skbuff. */
 	__u8			encapsulation:1;
 	__u8			encap_hdr_csum:1;
 	__u8			csum_valid:1;
@@ -598,6 +615,11 @@ struct sk_buff {
 		__u32		reserved_tailroom;
 	};
 
+	kmemcheck_bitfield_begin(flags3);
+	__u8			csum_level:2;
+	/* 14 bit hole */
+	kmemcheck_bitfield_end(flags3);
+
 	__be16			inner_protocol;
 	__u16			inner_transport_header;
 	__u16			inner_network_header;
@@ -1862,18 +1884,6 @@ static inline int pskb_network_may_pull(struct sk_buff *skb, unsigned int len)
 	return pskb_may_pull(skb, skb_network_offset(skb) + len);
 }
 
-static inline void skb_pop_rcv_encapsulation(struct sk_buff *skb)
-{
-	/* Only continue with checksum unnecessary if device indicated
-	 * it is valid across encapsulation (skb->encapsulation was set).
-	 */
-	if (skb->ip_summed == CHECKSUM_UNNECESSARY && !skb->encapsulation)
-		skb->ip_summed = CHECKSUM_NONE;
-
-	skb->encapsulation = 0;
-	skb->csum_valid = 0;
-}
-
 /*
  * CPUs often take a performance hit when accessing unaligned memory
  * locations. The actual performance hit varies, it can be small if the
@@ -2794,6 +2804,27 @@ static inline __sum16 skb_checksum_complete(struct sk_buff *skb)
 	       0 : __skb_checksum_complete(skb);
 }
 
+static inline void __skb_decr_checksum_unnecessary(struct sk_buff *skb)
+{
+	if (skb->ip_summed == CHECKSUM_UNNECESSARY) {
+		if (skb->csum_level == 0)
+			skb->ip_summed = CHECKSUM_NONE;
+		else
+			skb->csum_level--;
+	}
+}
+
+static inline void __skb_incr_checksum_unnecessary(struct sk_buff *skb)
+{
+	if (skb->ip_summed == CHECKSUM_UNNECESSARY) {
+		if (skb->csum_level < SKB_MAX_CSUM_LEVEL)
+			skb->csum_level++;
+	} else if (skb->ip_summed == CHECKSUM_NONE) {
+		skb->ip_summed = CHECKSUM_UNNECESSARY;
+		skb->csum_level = 0;
+	}
+}
+
 /* Check if we need to perform checksum complete validation.
  *
  * Returns true if checksum complete is needed, false otherwise
@@ -2805,6 +2836,7 @@ static inline bool __skb_checksum_validate_needed(struct sk_buff *skb,
 {
 	if (skb_csum_unnecessary(skb) || (zero_okay && !check)) {
 		skb->csum_valid = 1;
+		__skb_decr_checksum_unnecessary(skb);
 		return false;
 	}
 

net/core/dev.c

@@ -3962,13 +3962,6 @@ static enum gro_result dev_gro_receive(struct napi_struct *napi, struct sk_buff
 
 	gro_list_prepare(napi, skb);
 
-	if (skb->ip_summed == CHECKSUM_COMPLETE) {
-		NAPI_GRO_CB(skb)->csum = skb->csum;
-		NAPI_GRO_CB(skb)->csum_valid = 1;
-	} else {
-		NAPI_GRO_CB(skb)->csum_valid = 0;
-	}
-
 	rcu_read_lock();
 	list_for_each_entry_rcu(ptype, head, list) {
 		if (ptype->type != type || !ptype->callbacks.gro_receive)
@@ -3980,7 +3973,22 @@ static enum gro_result dev_gro_receive(struct napi_struct *napi, struct sk_buff
 		NAPI_GRO_CB(skb)->flush = 0;
 		NAPI_GRO_CB(skb)->free = 0;
 		NAPI_GRO_CB(skb)->udp_mark = 0;
-		NAPI_GRO_CB(skb)->encapsulation = 0;
+
+		/* Setup for GRO checksum validation */
+		switch (skb->ip_summed) {
+		case CHECKSUM_COMPLETE:
+			NAPI_GRO_CB(skb)->csum = skb->csum;
+			NAPI_GRO_CB(skb)->csum_valid = 1;
+			NAPI_GRO_CB(skb)->csum_cnt = 0;
+			break;
+		case CHECKSUM_UNNECESSARY:
+			NAPI_GRO_CB(skb)->csum_cnt = skb->csum_level + 1;
+			NAPI_GRO_CB(skb)->csum_valid = 0;
+			break;
+		default:
+			NAPI_GRO_CB(skb)->csum_cnt = 0;
+			NAPI_GRO_CB(skb)->csum_valid = 0;
+		}
 
 		pp = ptype->callbacks.gro_receive(&napi->gro_list, skb);
 		break;

net/ipv4/gre_demux.c

@@ -125,7 +125,6 @@ static int parse_gre_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
 			*csum_err = true;
 			return -EINVAL;
 		}
-		skb_pop_rcv_encapsulation(skb);
 		options++;
 	}
 

net/ipv4/gre_offload.c

@@ -172,12 +172,9 @@ static struct sk_buff **gre_gro_receive(struct sk_buff **head,
 	}
 
 	/* Don't bother verifying checksum if we're going to flush anyway. */
-	if (greh->flags & GRE_CSUM) {
-		if (!NAPI_GRO_CB(skb)->flush &&
-		    skb_gro_checksum_simple_validate(skb))
+	if ((greh->flags & GRE_CSUM) && !NAPI_GRO_CB(skb)->flush &&
+	    skb_gro_checksum_simple_validate(skb))
 			goto out_unlock;
-		NAPI_GRO_CB(skb)->encapsulation++;
-	}
 
 	flush = 0;
 

net/ipv4/udp_offload.c

@@ -238,12 +238,13 @@ struct sk_buff **udp_gro_receive(struct sk_buff **head, struct sk_buff *skb,
 	int flush = 1;
 
 	if (NAPI_GRO_CB(skb)->udp_mark ||
-	    (!skb->encapsulation && !NAPI_GRO_CB(skb)->csum_valid))
+	    (skb->ip_summed != CHECKSUM_PARTIAL &&
+	     NAPI_GRO_CB(skb)->csum_cnt == 0 &&
+	     !NAPI_GRO_CB(skb)->csum_valid))
 		goto out;
 
 	/* mark that this skb passed once through the udp gro layer */
 	NAPI_GRO_CB(skb)->udp_mark = 1;
-	NAPI_GRO_CB(skb)->encapsulation++;
 
 	rcu_read_lock();
 	uo_priv = rcu_dereference(udp_offload_base);

net/sctp/input.c

@@ -133,9 +133,13 @@ int sctp_rcv(struct sk_buff *skb)
 	__skb_pull(skb, skb_transport_offset(skb));
 	if (skb->len < sizeof(struct sctphdr))
 		goto discard_it;
-	if (!sctp_checksum_disable && !skb_csum_unnecessary(skb) &&
-		  sctp_rcv_checksum(net, skb) < 0)
+
+	skb->csum_valid = 0; /* Previous value not applicable */
+	if (skb_csum_unnecessary(skb))
+		__skb_decr_checksum_unnecessary(skb);
+	else if (!sctp_checksum_disable && sctp_rcv_checksum(net, skb) < 0)
 		goto discard_it;
+	skb->csum_valid = 1;
 
 	skb_pull(skb, sizeof(struct sctphdr));