From: Ilpo Järvinen <ij@xxxxxxxxxx>
Handling the CWR flag differs between RFC 3168 ECN and AccECN.
With RFC 3168 ECN aware TSO (NETIF_F_TSO_ECN) CWR flag is cleared
starting from 2nd segment which is incompatible how AccECN handles
the CWR flag. Such super-segments are indicated by SKB_GSO_TCP_ECN.
With AccECN, CWR flag (or more accurately, the ACE field that also
includes ECE & AE flags) changes only when new packet(s) with CE
mark arrives so the flag should not be changed within a super-skb.
The new skb/feature flags are necessary to prevent such TSO engines
corrupting AccECN ACE counters by clearing the CWR flag (if the
CWR handling feature cannot be turned off).
If NIC is completely unaware of RFC3168 ECN (doesn't support
NETIF_F_TSO_ECN) or its TSO engine can be set to not touch CWR flag
despite supporting also NETIF_F_TSO_ECN, TSO could be safely used
with AccECN on such NIC. This should be evaluated per NIC basis
(not done in this patch series for any NICs).
For the cases, where TSO cannot keep its hands off the CWR flag,
a GSO fallback is provided by this patch.
Signed-off-by: Ilpo Järvinen <ij@xxxxxxxxxx>
Signed-off-by: Chia-Yu Chang <chia-yu.chang@xxxxxxxxxxxxxxxxxxx>
Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
---
include/linux/netdev_features.h | 8 +++++---
include/linux/netdevice.h | 2 ++
include/linux/skbuff.h | 2 ++
net/ethtool/common.c | 1 +
net/ipv4/tcp_offload.c | 6 +++++-
5 files changed, 15 insertions(+), 4 deletions(-)
diff --git a/include/linux/netdev_features.h b/include/linux/netdev_features.h
index 11be70a7929f..7a01c518e573 100644
--- a/include/linux/netdev_features.h
+++ b/include/linux/netdev_features.h
@@ -53,12 +53,12 @@ enum {
NETIF_F_GSO_UDP_BIT, /* ... UFO, deprecated except tuntap */
NETIF_F_GSO_UDP_L4_BIT, /* ... UDP payload GSO (not UFO) */
NETIF_F_GSO_FRAGLIST_BIT, /* ... Fraglist GSO */
+ NETIF_F_GSO_ACCECN_BIT, /* TCP AccECN w/ TSO (no clear CWR) */
/**/NETIF_F_GSO_LAST = /* last bit, see GSO_MASK */
- NETIF_F_GSO_FRAGLIST_BIT,
+ NETIF_F_GSO_ACCECN_BIT,
NETIF_F_FCOE_CRC_BIT, /* FCoE CRC32 */
NETIF_F_SCTP_CRC_BIT, /* SCTP checksum offload */
- __UNUSED_NETIF_F_37,
NETIF_F_NTUPLE_BIT, /* N-tuple filters supported */
NETIF_F_RXHASH_BIT, /* Receive hashing offload */
NETIF_F_RXCSUM_BIT, /* Receive checksumming offload */
@@ -128,6 +128,7 @@ enum {
#define NETIF_F_SG __NETIF_F(SG)
#define NETIF_F_TSO6 __NETIF_F(TSO6)
#define NETIF_F_TSO_ECN __NETIF_F(TSO_ECN)
+#define NETIF_F_GSO_ACCECN __NETIF_F(GSO_ACCECN)
#define NETIF_F_TSO __NETIF_F(TSO)
#define NETIF_F_VLAN_CHALLENGED __NETIF_F(VLAN_CHALLENGED)
#define NETIF_F_RXFCS __NETIF_F(RXFCS)
@@ -210,7 +211,8 @@ static inline int find_next_netdev_feature(u64 feature, unsigned long start)
NETIF_F_TSO_ECN | NETIF_F_TSO_MANGLEID)
/* List of features with software fallbacks. */
-#define NETIF_F_GSO_SOFTWARE (NETIF_F_ALL_TSO | NETIF_F_GSO_SCTP | \
+#define NETIF_F_GSO_SOFTWARE (NETIF_F_ALL_TSO | \
+ NETIF_F_GSO_ACCECN | NETIF_F_GSO_SCTP | \
NETIF_F_GSO_UDP_L4 | NETIF_F_GSO_FRAGLIST)
/*
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index deffb9a0284f..e3742dfefad0 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -5140,6 +5140,8 @@ static inline bool net_gso_ok(netdev_features_t features, int gso_type)
BUILD_BUG_ON(SKB_GSO_UDP != (NETIF_F_GSO_UDP >> NETIF_F_GSO_SHIFT));
BUILD_BUG_ON(SKB_GSO_UDP_L4 != (NETIF_F_GSO_UDP_L4 >> NETIF_F_GSO_SHIFT));
BUILD_BUG_ON(SKB_GSO_FRAGLIST != (NETIF_F_GSO_FRAGLIST >> NETIF_F_GSO_SHIFT));
+ BUILD_BUG_ON(SKB_GSO_TCP_ACCECN !=
+ (NETIF_F_GSO_ACCECN >> NETIF_F_GSO_SHIFT));
return (features & feature) == feature;
}
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index bb2b751d274a..1367c2883478 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -703,6 +703,8 @@ enum {
SKB_GSO_UDP_L4 = 1 << 17,
SKB_GSO_FRAGLIST = 1 << 18,
+
+ SKB_GSO_TCP_ACCECN = 1 << 19,
};
#if BITS_PER_LONG > 32
diff --git a/net/ethtool/common.c b/net/ethtool/common.c
index 2607aea1fbfb..d6569fa35f36 100644
--- a/net/ethtool/common.c
+++ b/net/ethtool/common.c
@@ -35,6 +35,7 @@ const char netdev_features_strings[NETDEV_FEATURE_COUNT][ETH_GSTRING_LEN] = {
[NETIF_F_TSO_BIT] = "tx-tcp-segmentation",
[NETIF_F_GSO_ROBUST_BIT] = "tx-gso-robust",
[NETIF_F_TSO_ECN_BIT] = "tx-tcp-ecn-segmentation",
+ [NETIF_F_GSO_ACCECN_BIT] = "tx-tcp-accecn-segmentation",
[NETIF_F_TSO_MANGLEID_BIT] = "tx-tcp-mangleid-segmentation",
[NETIF_F_TSO6_BIT] = "tx-tcp6-segmentation",
[NETIF_F_FSO_BIT] = "tx-fcoe-segmentation",
diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
index 2308665b51c5..0b05f30e9e5f 100644
--- a/net/ipv4/tcp_offload.c
+++ b/net/ipv4/tcp_offload.c
@@ -139,6 +139,7 @@ struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
struct sk_buff *gso_skb = skb;
__sum16 newcheck;
bool ooo_okay, copy_destructor;
+ bool ecn_cwr_mask;
__wsum delta;
th = tcp_hdr(skb);
@@ -198,6 +199,8 @@ struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
newcheck = ~csum_fold(csum_add(csum_unfold(th->check), delta));
+ ecn_cwr_mask = !!(skb_shinfo(gso_skb)->gso_type & SKB_GSO_TCP_ACCECN);
+
while (skb->next) {
th->fin = th->psh = 0;
th->check = newcheck;
@@ -217,7 +220,8 @@ struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
th = tcp_hdr(skb);
th->seq = htonl(seq);
- th->cwr = 0;
+
+ th->cwr &= ecn_cwr_mask;
}
/* Following permits TCP Small Queues to work well with GSO :
--
2.34.1
