[PATCH net-next v4 0/5] net: gso: restore outer ip ids correctly

[PATCH net-next v4 0/5] net: gso: restore outer ip ids correctly

[Richard Gobert]

GRO currently ignores outer IPv4 header IDs for encapsulated packets
that have their don't-fragment flag set. GSO, however, always assumes
that outer IP IDs are incrementing. This results in GSO mangling the
outer IDs when they aren't incrementing. For example, GSO mangles the
outer IDs of IPv6 packets that were converted to IPv4, which must
have an ID of 0 according to RFC 6145, sect. 5.1.

GRO+GSO is supposed to be entirely transparent by default. GSO already
correctly restores inner IDs and IDs of non-encapsulated packets. The
tx-tcp-mangleid-segmentation feature can be enabled to allow the
mangling of such IDs so that TSO can be used.

This series fixes outer ID restoration for encapsulated packets when
tx-tcp-mangleid-segmentation is disabled. It also allows GRO to merge
packets with fixed IDs that don't have their don't-fragment flag set.

v3 -> v4:
  - Specify that mangleid for outer ids cannot turn incrementing ids to fixed if DF is unset
  - Update segmentation-offload documentation
  - Fix setting fixed ids in ef100 TSO
  - Reformat gro_receive_network_flush again

v2 -> v3:
 - Make argument const in fou_gro_ops helper
 - Rename SKB_GSO_TCP_FIXEDID_OUTER to SKB_GSO_TCP_FIXEDID
 - Fix formatting in selftest, gro_receive_network_flush and tcp4_gro_complete

v1 -> v2:
 - Add fou_gro_ops helper
 - Clarify why sk_family check works
 - Fix ipip packet generation in selftest

Links:
 - v1: https://lore.kernel.org/netdev/20250814114030.7683-1-richardbgobert@gmail.com/
 - v2: https://lore.kernel.org/netdev/20250819063223.5239-1-richardbgobert@gmail.com/
 - v3: https://lore.kernel.org/netdev/20250821073047.2091-1-richardbgobert@gmail.com/

Richard Gobert (5):
  net: gro: remove is_ipv6 from napi_gro_cb
  net: gro: only merge packets with incrementing or fixed outer ids
  net: gso: restore ids of outer ip headers correctly
  net: gro: remove unnecessary df checks
  selftests/net: test ipip packets in gro.sh

 .../networking/segmentation-offloads.rst      |  9 ++-
 .../net/ethernet/mellanox/mlx5/core/en_rx.c   |  8 ++-
 drivers/net/ethernet/sfc/ef100_tx.c           | 17 ++++--
 include/linux/netdevice.h                     |  9 ++-
 include/linux/skbuff.h                        |  6 +-
 include/net/gro.h                             | 36 +++++-------
 net/core/dev.c                                |  4 +-
 net/ipv4/af_inet.c                            | 10 +---
 net/ipv4/fou_core.c                           | 32 +++++-----
 net/ipv4/udp_offload.c                        |  2 -
 net/ipv6/udp_offload.c                        |  2 -
 tools/testing/selftests/net/gro.c             | 58 ++++++++++++++-----
 tools/testing/selftests/net/gro.sh            |  5 +-
 13 files changed, 117 insertions(+), 81 deletions(-)

-- 
2.36.1

[PATCH net-next v4 1/5] net: gro: remove is_ipv6 from napi_gro_cb

[Richard Gobert]

Remove is_ipv6 from napi_gro_cb and use sk->sk_family instead.
This frees up space for another ip_fixedid bit that will be added
in the next commit.

udp_sock_create always creates either a AP_INET or a AF_INET6 socket,
so using sk->sk_family is reliable. In IPv6-FOU, cfg-ipv6_v6only is
always enabled.

Signed-off-by: Richard Gobert <richardbgobert@gmail.com>
---
 include/net/gro.h      |  3 ---
 net/ipv4/fou_core.c    | 32 ++++++++++++++------------------
 net/ipv4/udp_offload.c |  2 --
 net/ipv6/udp_offload.c |  2 --
 4 files changed, 14 insertions(+), 25 deletions(-)

diff --git a/include/net/gro.h b/include/net/gro.h
index a0fca7ac6e7e..87c68007f949 100644
--- a/include/net/gro.h
+++ b/include/net/gro.h
@@ -71,9 +71,6 @@ struct napi_gro_cb {
 		/* Free the skb? */
 		u8	free:2;
 
-		/* Used in foo-over-udp, set in udp[46]_gro_receive */
-		u8	is_ipv6:1;
-
 		/* Used in GRE, set in fou/gue_gro_receive */
 		u8	is_fou:1;
 
diff --git a/net/ipv4/fou_core.c b/net/ipv4/fou_core.c
index 3e30745e2c09..a654a06ae7fd 100644
--- a/net/ipv4/fou_core.c
+++ b/net/ipv4/fou_core.c
@@ -228,21 +228,27 @@ static int gue_udp_recv(struct sock *sk, struct sk_buff *skb)
 	return 0;
 }
 
+static inline const struct net_offload *fou_gro_ops(const struct sock *sk,
+						    int proto)
+{
+	const struct net_offload __rcu **offloads;
+
+	/* FOU doesn't allow IPv4 on IPv6 sockets. */
+	offloads = sk->sk_family == AF_INET6 ? inet6_offloads : inet_offloads;
+	return rcu_dereference(offloads[proto]);
+}
+
 static struct sk_buff *fou_gro_receive(struct sock *sk,
 				       struct list_head *head,
 				       struct sk_buff *skb)
 {
-	const struct net_offload __rcu **offloads;
 	struct fou *fou = fou_from_sock(sk);
 	const struct net_offload *ops;
 	struct sk_buff *pp = NULL;
-	u8 proto;
 
 	if (!fou)
 		goto out;
 
-	proto = fou->protocol;
-
 	/* We can clear the encap_mark for FOU as we are essentially doing
 	 * one of two possible things.  We are either adding an L4 tunnel
 	 * header to the outer L3 tunnel header, or we are simply
@@ -254,8 +260,7 @@ static struct sk_buff *fou_gro_receive(struct sock *sk,
 	/* Flag this frame as already having an outer encap header */
 	NAPI_GRO_CB(skb)->is_fou = 1;
 
-	offloads = NAPI_GRO_CB(skb)->is_ipv6 ? inet6_offloads : inet_offloads;
-	ops = rcu_dereference(offloads[proto]);
+	ops = fou_gro_ops(sk, fou->protocol);
 	if (!ops || !ops->callbacks.gro_receive)
 		goto out;
 
@@ -268,10 +273,8 @@ static struct sk_buff *fou_gro_receive(struct sock *sk,
 static int fou_gro_complete(struct sock *sk, struct sk_buff *skb,
 			    int nhoff)
 {
-	const struct net_offload __rcu **offloads;
 	struct fou *fou = fou_from_sock(sk);
 	const struct net_offload *ops;
-	u8 proto;
 	int err;
 
 	if (!fou) {
@@ -279,10 +282,7 @@ static int fou_gro_complete(struct sock *sk, struct sk_buff *skb,
 		goto out;
 	}
 
-	proto = fou->protocol;
-
-	offloads = NAPI_GRO_CB(skb)->is_ipv6 ? inet6_offloads : inet_offloads;
-	ops = rcu_dereference(offloads[proto]);
+	ops = fou_gro_ops(sk, fou->protocol);
 	if (WARN_ON(!ops || !ops->callbacks.gro_complete)) {
 		err = -ENOSYS;
 		goto out;
@@ -323,7 +323,6 @@ static struct sk_buff *gue_gro_receive(struct sock *sk,
 				       struct list_head *head,
 				       struct sk_buff *skb)
 {
-	const struct net_offload __rcu **offloads;
 	const struct net_offload *ops;
 	struct sk_buff *pp = NULL;
 	struct sk_buff *p;
@@ -450,8 +449,7 @@ static struct sk_buff *gue_gro_receive(struct sock *sk,
 	/* Flag this frame as already having an outer encap header */
 	NAPI_GRO_CB(skb)->is_fou = 1;
 
-	offloads = NAPI_GRO_CB(skb)->is_ipv6 ? inet6_offloads : inet_offloads;
-	ops = rcu_dereference(offloads[proto]);
+	ops = fou_gro_ops(sk, proto);
 	if (!ops || !ops->callbacks.gro_receive)
 		goto out;
 
@@ -467,7 +465,6 @@ static struct sk_buff *gue_gro_receive(struct sock *sk,
 static int gue_gro_complete(struct sock *sk, struct sk_buff *skb, int nhoff)
 {
 	struct guehdr *guehdr = (struct guehdr *)(skb->data + nhoff);
-	const struct net_offload __rcu **offloads;
 	const struct net_offload *ops;
 	unsigned int guehlen = 0;
 	u8 proto;
@@ -494,8 +491,7 @@ static int gue_gro_complete(struct sock *sk, struct sk_buff *skb, int nhoff)
 		return err;
 	}
 
-	offloads = NAPI_GRO_CB(skb)->is_ipv6 ? inet6_offloads : inet_offloads;
-	ops = rcu_dereference(offloads[proto]);
+	ops = fou_gro_ops(sk, proto);
 	if (WARN_ON(!ops || !ops->callbacks.gro_complete))
 		goto out;
 
diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index b1f3fd302e9d..19d0b5b09ffa 100644
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -891,8 +891,6 @@ struct sk_buff *udp4_gro_receive(struct list_head *head, struct sk_buff *skb)
 		skb_gro_checksum_try_convert(skb, IPPROTO_UDP,
 					     inet_gro_compute_pseudo);
 skip:
-	NAPI_GRO_CB(skb)->is_ipv6 = 0;
-
 	if (static_branch_unlikely(&udp_encap_needed_key))
 		sk = udp4_gro_lookup_skb(skb, uh->source, uh->dest);
 
diff --git a/net/ipv6/udp_offload.c b/net/ipv6/udp_offload.c
index d8445ac1b2e4..046f13b1d77a 100644
--- a/net/ipv6/udp_offload.c
+++ b/net/ipv6/udp_offload.c
@@ -154,8 +154,6 @@ struct sk_buff *udp6_gro_receive(struct list_head *head, struct sk_buff *skb)
 					     ip6_gro_compute_pseudo);
 
 skip:
-	NAPI_GRO_CB(skb)->is_ipv6 = 1;
-
 	if (static_branch_unlikely(&udpv6_encap_needed_key))
 		sk = udp6_gro_lookup_skb(skb, uh->source, uh->dest);
 
-- 
2.36.1

[PATCH net-next v4 2/5] net: gro: only merge packets with incrementing or fixed outer ids

[Richard Gobert]

Only merge encapsulated packets if their outer IDs are either
incrementing or fixed, just like for inner IDs and IDs of non-encapsulated
packets.

Add another ip_fixedid bit for a total of two bits: one for outer IDs (and
for unencapsulated packets) and one for inner IDs.

This commit preserves the current behavior of GSO where only the IDs of the
inner-most headers are restored correctly.

Signed-off-by: Richard Gobert <richardbgobert@gmail.com>
---
 include/net/gro.h      | 30 +++++++++++++++---------------
 net/ipv4/tcp_offload.c |  5 ++++-
 2 files changed, 19 insertions(+), 16 deletions(-)

diff --git a/include/net/gro.h b/include/net/gro.h
index 87c68007f949..322c5517f508 100644
--- a/include/net/gro.h
+++ b/include/net/gro.h
@@ -75,7 +75,7 @@ struct napi_gro_cb {
 		u8	is_fou:1;
 
 		/* Used to determine if ipid_offset can be ignored */
-		u8	ip_fixedid:1;
+		u8	ip_fixedid:2;
 
 		/* Number of gro_receive callbacks this packet already went through */
 		u8 recursion_counter:4;
@@ -442,29 +442,26 @@ static inline __wsum ip6_gro_compute_pseudo(const struct sk_buff *skb,
 }
 
 static inline int inet_gro_flush(const struct iphdr *iph, const struct iphdr *iph2,
-				 struct sk_buff *p, bool outer)
+				 struct sk_buff *p, bool inner)
 {
 	const u32 id = ntohl(*(__be32 *)&iph->id);
 	const u32 id2 = ntohl(*(__be32 *)&iph2->id);
 	const u16 ipid_offset = (id >> 16) - (id2 >> 16);
 	const u16 count = NAPI_GRO_CB(p)->count;
 	const u32 df = id & IP_DF;
-	int flush;
 
 	/* All fields must match except length and checksum. */
-	flush = (iph->ttl ^ iph2->ttl) | (iph->tos ^ iph2->tos) | (df ^ (id2 & IP_DF));
-
-	if (flush | (outer && df))
-		return flush;
+	if ((iph->ttl ^ iph2->ttl) | (iph->tos ^ iph2->tos) | (df ^ (id2 & IP_DF)))
+		return true;
 
 	/* When we receive our second frame we can make a decision on if we
 	 * continue this flow as an atomic flow with a fixed ID or if we use
 	 * an incrementing ID.
 	 */
 	if (count == 1 && df && !ipid_offset)
-		NAPI_GRO_CB(p)->ip_fixedid = true;
+		NAPI_GRO_CB(p)->ip_fixedid |= 1 << inner;
 
-	return ipid_offset ^ (count * !NAPI_GRO_CB(p)->ip_fixedid);
+	return ipid_offset ^ (count * !(NAPI_GRO_CB(p)->ip_fixedid & (1 << inner)));
 }
 
 static inline int ipv6_gro_flush(const struct ipv6hdr *iph, const struct ipv6hdr *iph2)
@@ -479,7 +476,7 @@ static inline int ipv6_gro_flush(const struct ipv6hdr *iph, const struct ipv6hdr
 
 static inline int __gro_receive_network_flush(const void *th, const void *th2,
 					      struct sk_buff *p, const u16 diff,
-					      bool outer)
+					      bool inner)
 {
 	const void *nh = th - diff;
 	const void *nh2 = th2 - diff;
@@ -487,19 +484,22 @@ static inline int __gro_receive_network_flush(const void *th, const void *th2,
 	if (((struct iphdr *)nh)->version == 6)
 		return ipv6_gro_flush(nh, nh2);
 	else
-		return inet_gro_flush(nh, nh2, p, outer);
+		return inet_gro_flush(nh, nh2, p, inner);
 }
 
 static inline int gro_receive_network_flush(const void *th, const void *th2,
 					    struct sk_buff *p)
 {
-	const bool encap_mark = NAPI_GRO_CB(p)->encap_mark;
 	int off = skb_transport_offset(p);
 	int flush;
+	int diff;
 
-	flush = __gro_receive_network_flush(th, th2, p, off - NAPI_GRO_CB(p)->network_offset, encap_mark);
-	if (encap_mark)
-		flush |= __gro_receive_network_flush(th, th2, p, off - NAPI_GRO_CB(p)->inner_network_offset, false);
+	diff = off - NAPI_GRO_CB(p)->network_offset;
+	flush = __gro_receive_network_flush(th, th2, p, diff, false);
+	if (NAPI_GRO_CB(p)->encap_mark) {
+		diff = off - NAPI_GRO_CB(p)->inner_network_offset;
+		flush |= __gro_receive_network_flush(th, th2, p, diff, true);
+	}
 
 	return flush;
 }
diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
index e6612bd84d09..1949eede9ec9 100644
--- a/net/ipv4/tcp_offload.c
+++ b/net/ipv4/tcp_offload.c
@@ -471,6 +471,7 @@ INDIRECT_CALLABLE_SCOPE int tcp4_gro_complete(struct sk_buff *skb, int thoff)
 	const u16 offset = NAPI_GRO_CB(skb)->network_offsets[skb->encapsulation];
 	const struct iphdr *iph = (struct iphdr *)(skb->data + offset);
 	struct tcphdr *th = tcp_hdr(skb);
+	bool is_fixedid;
 
 	if (unlikely(NAPI_GRO_CB(skb)->is_flist)) {
 		skb_shinfo(skb)->gso_type |= SKB_GSO_FRAGLIST | SKB_GSO_TCPV4;
@@ -484,8 +485,10 @@ INDIRECT_CALLABLE_SCOPE int tcp4_gro_complete(struct sk_buff *skb, int thoff)
 	th->check = ~tcp_v4_check(skb->len - thoff, iph->saddr,
 				  iph->daddr, 0);
 
+	is_fixedid = (NAPI_GRO_CB(skb)->ip_fixedid >> skb->encapsulation) & 1;
+
 	skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV4 |
-			(NAPI_GRO_CB(skb)->ip_fixedid * SKB_GSO_TCP_FIXEDID);
+			(is_fixedid * SKB_GSO_TCP_FIXEDID);
 
 	tcp_gro_complete(skb);
 	return 0;
-- 
2.36.1

[PATCH net-next v4 3/5] net: gso: restore ids of outer ip headers correctly

[Richard Gobert]

Currently, NETIF_F_TSO_MANGLEID indicates that the inner-most ID can
be mangled. Outer IDs can always be mangled.

Make GSO preserve outer IDs by default, with NETIF_F_TSO_MANGLEID allowing
both inner and outer IDs to be mangled.

This commit also modifies a few drivers that use SKB_GSO_FIXEDID directly.

Signed-off-by: Richard Gobert <richardbgobert@gmail.com>
---
 .../networking/segmentation-offloads.rst        |  9 ++++-----
 drivers/net/ethernet/mellanox/mlx5/core/en_rx.c |  8 ++++++--
 drivers/net/ethernet/sfc/ef100_tx.c             | 17 +++++++++++++----
 include/linux/netdevice.h                       |  9 +++++++--
 include/linux/skbuff.h                          |  6 +++++-
 net/core/dev.c                                  |  4 +++-
 net/ipv4/af_inet.c                              | 13 ++++++-------
 net/ipv4/tcp_offload.c                          |  5 +----
 8 files changed, 45 insertions(+), 26 deletions(-)

diff --git a/Documentation/networking/segmentation-offloads.rst b/Documentation/networking/segmentation-offloads.rst
index 085e8fab03fd..d5dccfc6b82b 100644
--- a/Documentation/networking/segmentation-offloads.rst
+++ b/Documentation/networking/segmentation-offloads.rst
@@ -46,7 +46,9 @@ GSO type SKB_GSO_TCP_FIXEDID is specified then we will not increment the IP
 ID and all segments will use the same IP ID.  If a device has
 NETIF_F_TSO_MANGLEID set then the IP ID can be ignored when performing TSO
 and we will either increment the IP ID for all frames, or leave it at a
-static value based on driver preference.
+static value based on driver preference. For outer headers of encapsulated
+packets, the device drivers must guarantee that the IPv4 ID field is
+incremented in the case that a given header does not have the DF bit set.
 
 
 UDP Fragmentation Offload
@@ -124,10 +126,7 @@ Generic Receive Offload
 Generic receive offload is the complement to GSO.  Ideally any frame
 assembled by GRO should be segmented to create an identical sequence of
 frames using GSO, and any sequence of frames segmented by GSO should be
-able to be reassembled back to the original by GRO.  The only exception to
-this is IPv4 ID in the case that the DF bit is set for a given IP header.
-If the value of the IPv4 ID is not sequentially incrementing it will be
-altered so that it is when a frame assembled via GRO is segmented via GSO.
+able to be reassembled back to the original by GRO.
 
 
 Partial Generic Segmentation Offload
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
index b8c609d91d11..505c4ce7cef8 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
@@ -1289,8 +1289,12 @@ static void mlx5e_shampo_update_ipv4_tcp_hdr(struct mlx5e_rq *rq, struct iphdr *
 	tcp->check = ~tcp_v4_check(skb->len - tcp_off, ipv4->saddr,
 				   ipv4->daddr, 0);
 	skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV4;
-	if (ntohs(ipv4->id) == rq->hw_gro_data->second_ip_id)
-		skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_FIXEDID;
+	if (ntohs(ipv4->id) == rq->hw_gro_data->second_ip_id) {
+		bool encap = rq->hw_gro_data->fk.control.flags & FLOW_DIS_ENCAPSULATION;
+
+		skb_shinfo(skb)->gso_type |= encap ?
+					     SKB_GSO_TCP_FIXEDID_INNER : SKB_GSO_TCP_FIXEDID;
+	}
 
 	skb->csum_start = (unsigned char *)tcp - skb->head;
 	skb->csum_offset = offsetof(struct tcphdr, check);
diff --git a/drivers/net/ethernet/sfc/ef100_tx.c b/drivers/net/ethernet/sfc/ef100_tx.c
index e6b6be549581..24971346df00 100644
--- a/drivers/net/ethernet/sfc/ef100_tx.c
+++ b/drivers/net/ethernet/sfc/ef100_tx.c
@@ -190,6 +190,7 @@ static void ef100_make_tso_desc(struct efx_nic *efx,
 	bool gso_partial = skb_shinfo(skb)->gso_type & SKB_GSO_PARTIAL;
 	unsigned int len, ip_offset, tcp_offset, payload_segs;
 	u32 mangleid = ESE_GZ_TX_DESC_IP4_ID_INC_MOD16;
+	u32 mangleid_outer = ESE_GZ_TX_DESC_IP4_ID_INC_MOD16;
 	unsigned int outer_ip_offset, outer_l4_offset;
 	u16 vlan_tci = skb_vlan_tag_get(skb);
 	u32 mss = skb_shinfo(skb)->gso_size;
@@ -200,8 +201,17 @@ static void ef100_make_tso_desc(struct efx_nic *efx,
 	bool outer_csum;
 	u32 paylen;
 
-	if (skb_shinfo(skb)->gso_type & SKB_GSO_TCP_FIXEDID)
-		mangleid = ESE_GZ_TX_DESC_IP4_ID_NO_OP;
+	if (encap) {
+		if (skb_shinfo(skb)->gso_type & SKB_GSO_TCP_FIXEDID_INNER)
+			mangleid = ESE_GZ_TX_DESC_IP4_ID_NO_OP;
+		if (skb_shinfo(skb)->gso_type & SKB_GSO_TCP_FIXEDID)
+			mangleid_outer = ESE_GZ_TX_DESC_IP4_ID_NO_OP;
+	} else {
+		if (skb_shinfo(skb)->gso_type & SKB_GSO_TCP_FIXEDID)
+			mangleid = ESE_GZ_TX_DESC_IP4_ID_NO_OP;
+		mangleid_outer = ESE_GZ_TX_DESC_IP4_ID_NO_OP;
+	}
+
 	if (efx->net_dev->features & NETIF_F_HW_VLAN_CTAG_TX)
 		vlan_enable = skb_vlan_tag_present(skb);
 
@@ -245,8 +255,7 @@ static void ef100_make_tso_desc(struct efx_nic *efx,
 			      ESF_GZ_TX_TSO_OUTER_L4_OFF_W, outer_l4_offset >> 1,
 			      ESF_GZ_TX_TSO_ED_OUTER_UDP_LEN, udp_encap && !gso_partial,
 			      ESF_GZ_TX_TSO_ED_OUTER_IP_LEN, encap && !gso_partial,
-			      ESF_GZ_TX_TSO_ED_OUTER_IP4_ID, encap ? mangleid :
-								     ESE_GZ_TX_DESC_IP4_ID_NO_OP,
+			      ESF_GZ_TX_TSO_ED_OUTER_IP4_ID, mangleid_outer,
 			      ESF_GZ_TX_TSO_VLAN_INSERT_EN, vlan_enable,
 			      ESF_GZ_TX_TSO_VLAN_INSERT_TCI, vlan_tci
 		);
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index f3a3b761abfb..3d19c888b839 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -5290,13 +5290,18 @@ void skb_warn_bad_offload(const struct sk_buff *skb);
 
 static inline bool net_gso_ok(netdev_features_t features, int gso_type)
 {
-	netdev_features_t feature = (netdev_features_t)gso_type << NETIF_F_GSO_SHIFT;
+	netdev_features_t feature;
+
+	if (gso_type & (SKB_GSO_TCP_FIXEDID | SKB_GSO_TCP_FIXEDID_INNER))
+		gso_type |= __SKB_GSO_TCP_FIXEDID;
+
+	feature = ((netdev_features_t)gso_type << NETIF_F_GSO_SHIFT) & NETIF_F_GSO_MASK;
 
 	/* check flags correspondence */
 	BUILD_BUG_ON(SKB_GSO_TCPV4   != (NETIF_F_TSO >> NETIF_F_GSO_SHIFT));
 	BUILD_BUG_ON(SKB_GSO_DODGY   != (NETIF_F_GSO_ROBUST >> NETIF_F_GSO_SHIFT));
 	BUILD_BUG_ON(SKB_GSO_TCP_ECN != (NETIF_F_TSO_ECN >> NETIF_F_GSO_SHIFT));
-	BUILD_BUG_ON(SKB_GSO_TCP_FIXEDID != (NETIF_F_TSO_MANGLEID >> NETIF_F_GSO_SHIFT));
+	BUILD_BUG_ON(__SKB_GSO_TCP_FIXEDID != (NETIF_F_TSO_MANGLEID >> NETIF_F_GSO_SHIFT));
 	BUILD_BUG_ON(SKB_GSO_TCPV6   != (NETIF_F_TSO6 >> NETIF_F_GSO_SHIFT));
 	BUILD_BUG_ON(SKB_GSO_FCOE    != (NETIF_F_FSO >> NETIF_F_GSO_SHIFT));
 	BUILD_BUG_ON(SKB_GSO_GRE     != (NETIF_F_GSO_GRE >> NETIF_F_GSO_SHIFT));
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index ca8be45dd8be..cf95b325f9b4 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -674,7 +674,7 @@ enum {
 	/* This indicates the tcp segment has CWR set. */
 	SKB_GSO_TCP_ECN = 1 << 2,
 
-	SKB_GSO_TCP_FIXEDID = 1 << 3,
+	__SKB_GSO_TCP_FIXEDID = 1 << 3,
 
 	SKB_GSO_TCPV6 = 1 << 4,
 
@@ -707,6 +707,10 @@ enum {
 	SKB_GSO_FRAGLIST = 1 << 18,
 
 	SKB_GSO_TCP_ACCECN = 1 << 19,
+
+	/* These don't correspond with netdev features. */
+	SKB_GSO_TCP_FIXEDID = 1 << 30,
+	SKB_GSO_TCP_FIXEDID_INNER = 1 << 31,
 };
 
 #if BITS_PER_LONG > 32
diff --git a/net/core/dev.c b/net/core/dev.c
index 93a25d87b86b..f57c8dbf307f 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3769,7 +3769,9 @@ static netdev_features_t gso_features_check(const struct sk_buff *skb,
 		features &= ~dev->gso_partial_features;
 
 	/* Make sure to clear the IPv4 ID mangling feature if the
-	 * IPv4 header has the potential to be fragmented.
+	 * IPv4 header has the potential to be fragmented. For
+	 * encapsulated packets, the outer headers are guaranteed to
+	 * have incrementing IDs if DF is not set.
 	 */
 	if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4) {
 		struct iphdr *iph = skb->encapsulation ?
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 76e38092cd8a..fc7a6955fa0a 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1393,14 +1393,13 @@ struct sk_buff *inet_gso_segment(struct sk_buff *skb,
 
 	segs = ERR_PTR(-EPROTONOSUPPORT);
 
-	if (!skb->encapsulation || encap) {
-		udpfrag = !!(skb_shinfo(skb)->gso_type & SKB_GSO_UDP);
-		fixedid = !!(skb_shinfo(skb)->gso_type & SKB_GSO_TCP_FIXEDID);
+	/* fixed ID is invalid if DF bit is not set */
+	fixedid = !!(skb_shinfo(skb)->gso_type & (SKB_GSO_TCP_FIXEDID << encap));
+	if (fixedid && !(ip_hdr(skb)->frag_off & htons(IP_DF)))
+		goto out;
 
-		/* fixed ID is invalid if DF bit is not set */
-		if (fixedid && !(ip_hdr(skb)->frag_off & htons(IP_DF)))
-			goto out;
-	}
+	if (!skb->encapsulation || encap)
+		udpfrag = !!(skb_shinfo(skb)->gso_type & SKB_GSO_UDP);
 
 	ops = rcu_dereference(inet_offloads[proto]);
 	if (likely(ops && ops->callbacks.gso_segment)) {
diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
index 1949eede9ec9..e6612bd84d09 100644
--- a/net/ipv4/tcp_offload.c
+++ b/net/ipv4/tcp_offload.c
@@ -471,7 +471,6 @@ INDIRECT_CALLABLE_SCOPE int tcp4_gro_complete(struct sk_buff *skb, int thoff)
 	const u16 offset = NAPI_GRO_CB(skb)->network_offsets[skb->encapsulation];
 	const struct iphdr *iph = (struct iphdr *)(skb->data + offset);
 	struct tcphdr *th = tcp_hdr(skb);
-	bool is_fixedid;
 
 	if (unlikely(NAPI_GRO_CB(skb)->is_flist)) {
 		skb_shinfo(skb)->gso_type |= SKB_GSO_FRAGLIST | SKB_GSO_TCPV4;
@@ -485,10 +484,8 @@ INDIRECT_CALLABLE_SCOPE int tcp4_gro_complete(struct sk_buff *skb, int thoff)
 	th->check = ~tcp_v4_check(skb->len - thoff, iph->saddr,
 				  iph->daddr, 0);
 
-	is_fixedid = (NAPI_GRO_CB(skb)->ip_fixedid >> skb->encapsulation) & 1;
-
 	skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV4 |
-			(is_fixedid * SKB_GSO_TCP_FIXEDID);
+			(NAPI_GRO_CB(skb)->ip_fixedid * SKB_GSO_TCP_FIXEDID);
 
 	tcp_gro_complete(skb);
 	return 0;
-- 
2.36.1

[PATCH net-next v4 4/5] net: gro: remove unnecessary df checks

[Richard Gobert]

Currently, packets with fixed IDs will be merged only if their
don't-fragment bit is set. Merged packets are re-split into segments
before being fragmented, so the result is the same as if the packets
weren't merged to begin with.

Remove unnecessary don't-fragment checks.

Signed-off-by: Richard Gobert <richardbgobert@gmail.com>
---
 include/net/gro.h                 | 5 ++---
 net/ipv4/af_inet.c                | 3 ---
 tools/testing/selftests/net/gro.c | 9 ++++-----
 3 files changed, 6 insertions(+), 11 deletions(-)

diff --git a/include/net/gro.h b/include/net/gro.h
index 322c5517f508..691f267b3969 100644
--- a/include/net/gro.h
+++ b/include/net/gro.h
@@ -448,17 +448,16 @@ static inline int inet_gro_flush(const struct iphdr *iph, const struct iphdr *ip
 	const u32 id2 = ntohl(*(__be32 *)&iph2->id);
 	const u16 ipid_offset = (id >> 16) - (id2 >> 16);
 	const u16 count = NAPI_GRO_CB(p)->count;
-	const u32 df = id & IP_DF;
 
 	/* All fields must match except length and checksum. */
-	if ((iph->ttl ^ iph2->ttl) | (iph->tos ^ iph2->tos) | (df ^ (id2 & IP_DF)))
+	if ((iph->ttl ^ iph2->ttl) | (iph->tos ^ iph2->tos) | ((id ^ id2) & IP_DF))
 		return true;
 
 	/* When we receive our second frame we can make a decision on if we
 	 * continue this flow as an atomic flow with a fixed ID or if we use
 	 * an incrementing ID.
 	 */
-	if (count == 1 && df && !ipid_offset)
+	if (count == 1 && !ipid_offset)
 		NAPI_GRO_CB(p)->ip_fixedid |= 1 << inner;
 
 	return ipid_offset ^ (count * !(NAPI_GRO_CB(p)->ip_fixedid & (1 << inner)));
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index fc7a6955fa0a..c0542d9187e2 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1393,10 +1393,7 @@ struct sk_buff *inet_gso_segment(struct sk_buff *skb,
 
 	segs = ERR_PTR(-EPROTONOSUPPORT);
 
-	/* fixed ID is invalid if DF bit is not set */
 	fixedid = !!(skb_shinfo(skb)->gso_type & (SKB_GSO_TCP_FIXEDID << encap));
-	if (fixedid && !(ip_hdr(skb)->frag_off & htons(IP_DF)))
-		goto out;
 
 	if (!skb->encapsulation || encap)
 		udpfrag = !!(skb_shinfo(skb)->gso_type & SKB_GSO_UDP);
diff --git a/tools/testing/selftests/net/gro.c b/tools/testing/selftests/net/gro.c
index d5824eadea10..3d4a82a2607c 100644
--- a/tools/testing/selftests/net/gro.c
+++ b/tools/testing/selftests/net/gro.c
@@ -670,7 +670,7 @@ static void send_flush_id_case(int fd, struct sockaddr_ll *daddr, int tcase)
 		iph2->id = htons(9);
 		break;
 
-	case 3: /* DF=0, Fixed - should not coalesce */
+	case 3: /* DF=0, Fixed - should coalesce */
 		iph1->frag_off &= ~htons(IP_DF);
 		iph1->id = htons(8);
 
@@ -1188,10 +1188,9 @@ static void gro_receiver(void)
 			correct_payload[0] = PAYLOAD_LEN * 2;
 			check_recv_pkts(rxfd, correct_payload, 1);
 
-			printf("DF=0, Fixed - should not coalesce: ");
-			correct_payload[0] = PAYLOAD_LEN;
-			correct_payload[1] = PAYLOAD_LEN;
-			check_recv_pkts(rxfd, correct_payload, 2);
+			printf("DF=0, Fixed - should coalesce: ");
+			correct_payload[0] = PAYLOAD_LEN * 2;
+			check_recv_pkts(rxfd, correct_payload, 1);
 
 			printf("DF=1, 2 Incrementing and one fixed - should coalesce only first 2 packets: ");
 			correct_payload[0] = PAYLOAD_LEN * 2;
-- 
2.36.1

[PATCH net-next v4 5/5] selftests/net: test ipip packets in gro.sh

[Richard Gobert]

Add IPIP test-cases to the GRO selftest.

This selftest already contains IP ID test-cases. They are now
also tested for encapsulated packets.

This commit also fixes ipip packet generation in the test.

Signed-off-by: Richard Gobert <richardbgobert@gmail.com>
---
 tools/testing/selftests/net/gro.c  | 49 ++++++++++++++++++++++++------
 tools/testing/selftests/net/gro.sh |  5 +--
 2 files changed, 42 insertions(+), 12 deletions(-)

diff --git a/tools/testing/selftests/net/gro.c b/tools/testing/selftests/net/gro.c
index 3d4a82a2607c..451dc1c1eac5 100644
--- a/tools/testing/selftests/net/gro.c
+++ b/tools/testing/selftests/net/gro.c
@@ -93,6 +93,7 @@ static bool tx_socket = true;
 static int tcp_offset = -1;
 static int total_hdr_len = -1;
 static int ethhdr_proto = -1;
+static bool ipip;
 static const int num_flush_id_cases = 6;
 
 static void vlog(const char *fmt, ...)
@@ -114,7 +115,9 @@ static void setup_sock_filter(int fd)
 	int ipproto_off, opt_ipproto_off;
 	int next_off;
 
-	if (proto == PF_INET)
+	if (ipip)
+		next_off = sizeof(struct iphdr) + offsetof(struct iphdr, protocol);
+	else if (proto == PF_INET)
 		next_off = offsetof(struct iphdr, protocol);
 	else
 		next_off = offsetof(struct ipv6hdr, nexthdr);
@@ -244,7 +247,7 @@ static void fill_datalinklayer(void *buf)
 	eth->h_proto = ethhdr_proto;
 }
 
-static void fill_networklayer(void *buf, int payload_len)
+static void fill_networklayer(void *buf, int payload_len, int protocol)
 {
 	struct ipv6hdr *ip6h = buf;
 	struct iphdr *iph = buf;
@@ -254,7 +257,7 @@ static void fill_networklayer(void *buf, int payload_len)
 
 		ip6h->version = 6;
 		ip6h->payload_len = htons(sizeof(struct tcphdr) + payload_len);
-		ip6h->nexthdr = IPPROTO_TCP;
+		ip6h->nexthdr = protocol;
 		ip6h->hop_limit = 8;
 		if (inet_pton(AF_INET6, addr6_src, &ip6h->saddr) != 1)
 			error(1, errno, "inet_pton source ip6");
@@ -266,7 +269,7 @@ static void fill_networklayer(void *buf, int payload_len)
 		iph->version = 4;
 		iph->ihl = 5;
 		iph->ttl = 8;
-		iph->protocol	= IPPROTO_TCP;
+		iph->protocol	= protocol;
 		iph->tot_len = htons(sizeof(struct tcphdr) +
 				payload_len + sizeof(struct iphdr));
 		iph->frag_off = htons(0x4000); /* DF = 1, MF = 0 */
@@ -313,9 +316,19 @@ static void create_packet(void *buf, int seq_offset, int ack_offset,
 {
 	memset(buf, 0, total_hdr_len);
 	memset(buf + total_hdr_len, 'a', payload_len);
+
 	fill_transportlayer(buf + tcp_offset, seq_offset, ack_offset,
 			    payload_len, fin);
-	fill_networklayer(buf + ETH_HLEN, payload_len);
+
+	if (ipip) {
+		fill_networklayer(buf + ETH_HLEN + sizeof(struct iphdr),
+				  payload_len, IPPROTO_TCP);
+		fill_networklayer(buf + ETH_HLEN, payload_len + sizeof(struct iphdr),
+				  IPPROTO_IPIP);
+	} else {
+		fill_networklayer(buf + ETH_HLEN, payload_len, IPPROTO_TCP);
+	}
+
 	fill_datalinklayer(buf);
 }
 
@@ -416,6 +429,13 @@ static void recompute_packet(char *buf, char *no_ext, int extlen)
 		iph->tot_len = htons(ntohs(iph->tot_len) + extlen);
 		iph->check = 0;
 		iph->check = checksum_fold(iph, sizeof(struct iphdr), 0);
+
+		if (ipip) {
+			iph += 1;
+			iph->tot_len = htons(ntohs(iph->tot_len) + extlen);
+			iph->check = 0;
+			iph->check = checksum_fold(iph, sizeof(struct iphdr), 0);
+		}
 	} else {
 		ip6h->payload_len = htons(ntohs(ip6h->payload_len) + extlen);
 	}
@@ -777,7 +797,7 @@ static void send_fragment4(int fd, struct sockaddr_ll *daddr)
 	 */
 	memset(buf + total_hdr_len, 'a', PAYLOAD_LEN * 2);
 	fill_transportlayer(buf + tcp_offset, PAYLOAD_LEN, 0, PAYLOAD_LEN * 2, 0);
-	fill_networklayer(buf + ETH_HLEN, PAYLOAD_LEN);
+	fill_networklayer(buf + ETH_HLEN, PAYLOAD_LEN, IPPROTO_TCP);
 	fill_datalinklayer(buf);
 
 	iph->frag_off = htons(0x6000); // DF = 1, MF = 1
@@ -1071,7 +1091,7 @@ static void gro_sender(void)
 		 * and min ipv6hdr size. Like MAX_HDR_SIZE,
 		 * MAX_PAYLOAD is defined with the larger header of the two.
 		 */
-		int offset = proto == PF_INET ? 20 : 0;
+		int offset = (proto == PF_INET && !ipip) ? 20 : 0;
 		int remainder = (MAX_PAYLOAD + offset) % MSS;
 
 		send_large(txfd, &daddr, remainder);
@@ -1221,7 +1241,7 @@ static void gro_receiver(void)
 			check_recv_pkts(rxfd, correct_payload, 2);
 		}
 	} else if (strcmp(testname, "large") == 0) {
-		int offset = proto == PF_INET ? 20 : 0;
+		int offset = (proto == PF_INET && !ipip) ? 20 : 0;
 		int remainder = (MAX_PAYLOAD + offset) % MSS;
 
 		correct_payload[0] = (MAX_PAYLOAD + offset);
@@ -1250,6 +1270,7 @@ static void parse_args(int argc, char **argv)
 		{ "iface", required_argument, NULL, 'i' },
 		{ "ipv4", no_argument, NULL, '4' },
 		{ "ipv6", no_argument, NULL, '6' },
+		{ "ipip", no_argument, NULL, 'e' },
 		{ "rx", no_argument, NULL, 'r' },
 		{ "saddr", required_argument, NULL, 's' },
 		{ "smac", required_argument, NULL, 'S' },
@@ -1259,7 +1280,7 @@ static void parse_args(int argc, char **argv)
 	};
 	int c;
 
-	while ((c = getopt_long(argc, argv, "46d:D:i:rs:S:t:v", opts, NULL)) != -1) {
+	while ((c = getopt_long(argc, argv, "46d:D:ei:rs:S:t:v", opts, NULL)) != -1) {
 		switch (c) {
 		case '4':
 			proto = PF_INET;
@@ -1269,6 +1290,11 @@ static void parse_args(int argc, char **argv)
 			proto = PF_INET6;
 			ethhdr_proto = htons(ETH_P_IPV6);
 			break;
+		case 'e':
+			ipip = true;
+			proto = PF_INET;
+			ethhdr_proto = htons(ETH_P_IP);
+			break;
 		case 'd':
 			addr4_dst = addr6_dst = optarg;
 			break;
@@ -1304,7 +1330,10 @@ int main(int argc, char **argv)
 {
 	parse_args(argc, argv);
 
-	if (proto == PF_INET) {
+	if (ipip) {
+		tcp_offset = ETH_HLEN + sizeof(struct iphdr) * 2;
+		total_hdr_len = tcp_offset + sizeof(struct tcphdr);
+	} else if (proto == PF_INET) {
 		tcp_offset = ETH_HLEN + sizeof(struct iphdr);
 		total_hdr_len = tcp_offset + sizeof(struct tcphdr);
 	} else if (proto == PF_INET6) {
diff --git a/tools/testing/selftests/net/gro.sh b/tools/testing/selftests/net/gro.sh
index 9e3f186bc2a1..d16ec365b3cf 100755
--- a/tools/testing/selftests/net/gro.sh
+++ b/tools/testing/selftests/net/gro.sh
@@ -4,7 +4,7 @@
 readonly SERVER_MAC="aa:00:00:00:00:02"
 readonly CLIENT_MAC="aa:00:00:00:00:01"
 readonly TESTS=("data" "ack" "flags" "tcp" "ip" "large")
-readonly PROTOS=("ipv4" "ipv6")
+readonly PROTOS=("ipv4" "ipv6" "ipip")
 dev=""
 test="all"
 proto="ipv4"
@@ -31,7 +31,8 @@ run_test() {
       1>>log.txt
     wait "${server_pid}"
     exit_code=$?
-    if [[ ${test} == "large" && -n "${KSFT_MACHINE_SLOW}" && \
+    if [[ ( ${test} == "large" || ${protocol} == "ipip" ) && \
+          -n "${KSFT_MACHINE_SLOW}" && \
           ${exit_code} -ne 0 ]]; then
         echo "Ignoring errors due to slow environment" 1>&2
         exit_code=0
-- 
2.36.1

Re: [PATCH net-next v4 3/5] net: gso: restore ids of outer ip headers correctly

[Edward Cree]

On 01/09/2025 12:38, Richard Gobert wrote:
> Currently, NETIF_F_TSO_MANGLEID indicates that the inner-most ID can
> be mangled. Outer IDs can always be mangled.
> 
> Make GSO preserve outer IDs by default, with NETIF_F_TSO_MANGLEID allowing
> both inner and outer IDs to be mangled.
> 
> This commit also modifies a few drivers that use SKB_GSO_FIXEDID directly.
> 
> Signed-off-by: Richard Gobert <richardbgobert@gmail.com>
> ---
> diff --git a/drivers/net/ethernet/sfc/ef100_tx.c b/drivers/net/ethernet/sfc/ef100_tx.c
> index e6b6be549581..24971346df00 100644
> --- a/drivers/net/ethernet/sfc/ef100_tx.c
> +++ b/drivers/net/ethernet/sfc/ef100_tx.c
> @@ -190,6 +190,7 @@ static void ef100_make_tso_desc(struct efx_nic *efx,
>  	bool gso_partial = skb_shinfo(skb)->gso_type & SKB_GSO_PARTIAL;
>  	unsigned int len, ip_offset, tcp_offset, payload_segs;
>  	u32 mangleid = ESE_GZ_TX_DESC_IP4_ID_INC_MOD16;
> +	u32 mangleid_outer = ESE_GZ_TX_DESC_IP4_ID_INC_MOD16;
>  	unsigned int outer_ip_offset, outer_l4_offset;
>  	u16 vlan_tci = skb_vlan_tag_get(skb);
>  	u32 mss = skb_shinfo(skb)->gso_size;

Reverse xmas tree.
With that fixed you can add my Reviewed-by: Edward Cree <ecree.xilinx@gmail.com> # for sfc

Re: [PATCH net-next v4 1/5] net: gro: remove is_ipv6 from napi_gro_cb

[Willem de Bruijn]

Richard Gobert wrote:
> Remove is_ipv6 from napi_gro_cb and use sk->sk_family instead.
> This frees up space for another ip_fixedid bit that will be added
> in the next commit.
> 
> udp_sock_create always creates either a AP_INET or a AF_INET6 socket,
> so using sk->sk_family is reliable. In IPv6-FOU, cfg-ipv6_v6only is
> always enabled.
> 
> Signed-off-by: Richard Gobert <richardbgobert@gmail.com>
> ---
>  include/net/gro.h      |  3 ---
>  net/ipv4/fou_core.c    | 32 ++++++++++++++------------------
>  net/ipv4/udp_offload.c |  2 --
>  net/ipv6/udp_offload.c |  2 --
>  4 files changed, 14 insertions(+), 25 deletions(-)
> 
> diff --git a/include/net/gro.h b/include/net/gro.h
> index a0fca7ac6e7e..87c68007f949 100644
> --- a/include/net/gro.h
> +++ b/include/net/gro.h
> @@ -71,9 +71,6 @@ struct napi_gro_cb {
>  		/* Free the skb? */
>  		u8	free:2;
>  
> -		/* Used in foo-over-udp, set in udp[46]_gro_receive */
> -		u8	is_ipv6:1;
> -
>  		/* Used in GRE, set in fou/gue_gro_receive */
>  		u8	is_fou:1;
>  
> diff --git a/net/ipv4/fou_core.c b/net/ipv4/fou_core.c
> index 3e30745e2c09..a654a06ae7fd 100644
> --- a/net/ipv4/fou_core.c
> +++ b/net/ipv4/fou_core.c
> @@ -228,21 +228,27 @@ static int gue_udp_recv(struct sock *sk, struct sk_buff *skb)
>  	return 0;
>  }
>  
> +static inline const struct net_offload *fou_gro_ops(const struct sock *sk,
> +						    int proto)

no explicit inline keyword in .c files

otherwise patch LGTM.

Re: [PATCH net-next v4 2/5] net: gro: only merge packets with incrementing or fixed outer ids

[Willem de Bruijn]

Richard Gobert wrote:
> Only merge encapsulated packets if their outer IDs are either
> incrementing or fixed, just like for inner IDs and IDs of non-encapsulated
> packets.
> 
> Add another ip_fixedid bit for a total of two bits: one for outer IDs (and
> for unencapsulated packets) and one for inner IDs.
> 
> This commit preserves the current behavior of GSO where only the IDs of the
> inner-most headers are restored correctly.
> 
> Signed-off-by: Richard Gobert <richardbgobert@gmail.com>
> ---
>  include/net/gro.h      | 30 +++++++++++++++---------------
>  net/ipv4/tcp_offload.c |  5 ++++-
>  2 files changed, 19 insertions(+), 16 deletions(-)
> 
> diff --git a/include/net/gro.h b/include/net/gro.h
> index 87c68007f949..322c5517f508 100644
> --- a/include/net/gro.h
> +++ b/include/net/gro.h
> @@ -75,7 +75,7 @@ struct napi_gro_cb {
>  		u8	is_fou:1;
>  
>  		/* Used to determine if ipid_offset can be ignored */
> -		u8	ip_fixedid:1;
> +		u8	ip_fixedid:2;
>  
>  		/* Number of gro_receive callbacks this packet already went through */
>  		u8 recursion_counter:4;
> @@ -442,29 +442,26 @@ static inline __wsum ip6_gro_compute_pseudo(const struct sk_buff *skb,
>  }
>  
>  static inline int inet_gro_flush(const struct iphdr *iph, const struct iphdr *iph2,
> -				 struct sk_buff *p, bool outer)
> +				 struct sk_buff *p, bool inner)
>  {
>  	const u32 id = ntohl(*(__be32 *)&iph->id);
>  	const u32 id2 = ntohl(*(__be32 *)&iph2->id);
>  	const u16 ipid_offset = (id >> 16) - (id2 >> 16);
>  	const u16 count = NAPI_GRO_CB(p)->count;
>  	const u32 df = id & IP_DF;
> -	int flush;
>  
>  	/* All fields must match except length and checksum. */
> -	flush = (iph->ttl ^ iph2->ttl) | (iph->tos ^ iph2->tos) | (df ^ (id2 & IP_DF));
> -
> -	if (flush | (outer && df))
> -		return flush;
> +	if ((iph->ttl ^ iph2->ttl) | (iph->tos ^ iph2->tos) | (df ^ (id2 & IP_DF)))
> +		return true;
>  
>  	/* When we receive our second frame we can make a decision on if we
>  	 * continue this flow as an atomic flow with a fixed ID or if we use
>  	 * an incrementing ID.
>  	 */
>  	if (count == 1 && df && !ipid_offset)
> -		NAPI_GRO_CB(p)->ip_fixedid = true;
> +		NAPI_GRO_CB(p)->ip_fixedid |= 1 << inner;
>  
> -	return ipid_offset ^ (count * !NAPI_GRO_CB(p)->ip_fixedid);
> +	return ipid_offset ^ (count * !(NAPI_GRO_CB(p)->ip_fixedid & (1 << inner)));
>  }
>  
>  static inline int ipv6_gro_flush(const struct ipv6hdr *iph, const struct ipv6hdr *iph2)
> @@ -479,7 +476,7 @@ static inline int ipv6_gro_flush(const struct ipv6hdr *iph, const struct ipv6hdr
>  
>  static inline int __gro_receive_network_flush(const void *th, const void *th2,
>  					      struct sk_buff *p, const u16 diff,
> -					      bool outer)
> +					      bool inner)
>  {
>  	const void *nh = th - diff;
>  	const void *nh2 = th2 - diff;
> @@ -487,19 +484,22 @@ static inline int __gro_receive_network_flush(const void *th, const void *th2,
>  	if (((struct iphdr *)nh)->version == 6)
>  		return ipv6_gro_flush(nh, nh2);
>  	else
> -		return inet_gro_flush(nh, nh2, p, outer);
> +		return inet_gro_flush(nh, nh2, p, inner);
>  }
>  
>  static inline int gro_receive_network_flush(const void *th, const void *th2,
>  					    struct sk_buff *p)
>  {
> -	const bool encap_mark = NAPI_GRO_CB(p)->encap_mark;
>  	int off = skb_transport_offset(p);
>  	int flush;
> +	int diff;
>  
> -	flush = __gro_receive_network_flush(th, th2, p, off - NAPI_GRO_CB(p)->network_offset, encap_mark);
> -	if (encap_mark)
> -		flush |= __gro_receive_network_flush(th, th2, p, off - NAPI_GRO_CB(p)->inner_network_offset, false);
> +	diff = off - NAPI_GRO_CB(p)->network_offset;
> +	flush = __gro_receive_network_flush(th, th2, p, diff, false);
> +	if (NAPI_GRO_CB(p)->encap_mark) {
> +		diff = off - NAPI_GRO_CB(p)->inner_network_offset;
> +		flush |= __gro_receive_network_flush(th, th2, p, diff, true);
> +	}

nit: this diff introduction is not needed. The patch is easier to
parse without the change. Even if line length will (still) be longer.

>  
>  	return flush;
>  }
> diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
> index e6612bd84d09..1949eede9ec9 100644
> --- a/net/ipv4/tcp_offload.c
> +++ b/net/ipv4/tcp_offload.c
> @@ -471,6 +471,7 @@ INDIRECT_CALLABLE_SCOPE int tcp4_gro_complete(struct sk_buff *skb, int thoff)
>  	const u16 offset = NAPI_GRO_CB(skb)->network_offsets[skb->encapsulation];
>  	const struct iphdr *iph = (struct iphdr *)(skb->data + offset);
>  	struct tcphdr *th = tcp_hdr(skb);
> +	bool is_fixedid;
>  
>  	if (unlikely(NAPI_GRO_CB(skb)->is_flist)) {
>  		skb_shinfo(skb)->gso_type |= SKB_GSO_FRAGLIST | SKB_GSO_TCPV4;
> @@ -484,8 +485,10 @@ INDIRECT_CALLABLE_SCOPE int tcp4_gro_complete(struct sk_buff *skb, int thoff)
>  	th->check = ~tcp_v4_check(skb->len - thoff, iph->saddr,
>  				  iph->daddr, 0);
>  
> +	is_fixedid = (NAPI_GRO_CB(skb)->ip_fixedid >> skb->encapsulation) & 1;
> +
>  	skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV4 |
> -			(NAPI_GRO_CB(skb)->ip_fixedid * SKB_GSO_TCP_FIXEDID);
> +			(is_fixedid * SKB_GSO_TCP_FIXEDID);

Similar to how gro_receive_network_flush is called from both transport
layers, TCP and UDP, this is needed in udp_gro_complete_segment too?

Existing equivalent block is entirely missing there.

The deeper issue is that this is named TCP_FIXEDID, but in reality it
is IPV4_FIXEDID and applies to all transport layer protocols on top.

Perhaps not to fix in this series. But a limitation of USO in the
meantime.

>  
>  	tcp_gro_complete(skb);
>  	return 0;
> -- 
> 2.36.1
> 

Re: [PATCH net-next v4 3/5] net: gso: restore ids of outer ip headers correctly

[Willem de Bruijn]

Richard Gobert wrote:
> Currently, NETIF_F_TSO_MANGLEID indicates that the inner-most ID can
> be mangled. Outer IDs can always be mangled.
> 
> Make GSO preserve outer IDs by default, with NETIF_F_TSO_MANGLEID allowing
> both inner and outer IDs to be mangled.
> 
> This commit also modifies a few drivers that use SKB_GSO_FIXEDID directly.
> 
> Signed-off-by: Richard Gobert <richardbgobert@gmail.com>
> ---
>  .../networking/segmentation-offloads.rst        |  9 ++++-----
>  drivers/net/ethernet/mellanox/mlx5/core/en_rx.c |  8 ++++++--
>  drivers/net/ethernet/sfc/ef100_tx.c             | 17 +++++++++++++----
>  include/linux/netdevice.h                       |  9 +++++++--
>  include/linux/skbuff.h                          |  6 +++++-
>  net/core/dev.c                                  |  4 +++-
>  net/ipv4/af_inet.c                              | 13 ++++++-------
>  net/ipv4/tcp_offload.c                          |  5 +----
>  8 files changed, 45 insertions(+), 26 deletions(-)
> 
> diff --git a/Documentation/networking/segmentation-offloads.rst b/Documentation/networking/segmentation-offloads.rst
> index 085e8fab03fd..d5dccfc6b82b 100644
> --- a/Documentation/networking/segmentation-offloads.rst
> +++ b/Documentation/networking/segmentation-offloads.rst
> @@ -46,7 +46,9 @@ GSO type SKB_GSO_TCP_FIXEDID is specified then we will not increment the IP
>  ID and all segments will use the same IP ID.  If a device has
>  NETIF_F_TSO_MANGLEID set then the IP ID can be ignored when performing TSO
>  and we will either increment the IP ID for all frames, or leave it at a
> -static value based on driver preference.
> +static value based on driver preference. For outer headers of encapsulated
> +packets, the device drivers must guarantee that the IPv4 ID field is
> +incremented in the case that a given header does not have the DF bit set.

Please split this into three paragraphs on FIXEDID, FIXED_INNER and
MANGLEID.

Specifically the use of FIXEDID to mean uncapped or outer should be
explicitly mentioned (as discussed previously).

Also, I understood that MANGLEID now means that both inner and outer
IP ID can be mangled. But this comment appears to say otherwise.
Maybe it helps to be more explicit also about behavior without DF.

>  Partial Generic Segmentation Offload
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
> index b8c609d91d11..505c4ce7cef8 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c

> diff --git a/drivers/net/ethernet/sfc/ef100_tx.c b/drivers/net/ethernet/sfc/ef100_tx.c
> index e6b6be549581..24971346df00 100644
> --- a/drivers/net/ethernet/sfc/ef100_tx.c
> +++ b/drivers/net/ethernet/sfc/ef100_tx.c

Not sure whether these driver changes need to be separate patches.

> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index f3a3b761abfb..3d19c888b839 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -5290,13 +5290,18 @@ void skb_warn_bad_offload(const struct sk_buff *skb);
>  
>  static inline bool net_gso_ok(netdev_features_t features, int gso_type)
>  {
> -	netdev_features_t feature = (netdev_features_t)gso_type << NETIF_F_GSO_SHIFT;
> +	netdev_features_t feature;
> +
> +	if (gso_type & (SKB_GSO_TCP_FIXEDID | SKB_GSO_TCP_FIXEDID_INNER))
> +		gso_type |= __SKB_GSO_TCP_FIXEDID;
> +
> +	feature = ((netdev_features_t)gso_type << NETIF_F_GSO_SHIFT) & NETIF_F_GSO_MASK;
>  
>  	/* check flags correspondence */
>  	BUILD_BUG_ON(SKB_GSO_TCPV4   != (NETIF_F_TSO >> NETIF_F_GSO_SHIFT));
>  	BUILD_BUG_ON(SKB_GSO_DODGY   != (NETIF_F_GSO_ROBUST >> NETIF_F_GSO_SHIFT));
>  	BUILD_BUG_ON(SKB_GSO_TCP_ECN != (NETIF_F_TSO_ECN >> NETIF_F_GSO_SHIFT));
> -	BUILD_BUG_ON(SKB_GSO_TCP_FIXEDID != (NETIF_F_TSO_MANGLEID >> NETIF_F_GSO_SHIFT));
> +	BUILD_BUG_ON(__SKB_GSO_TCP_FIXEDID != (NETIF_F_TSO_MANGLEID >> NETIF_F_GSO_SHIFT));
>  	BUILD_BUG_ON(SKB_GSO_TCPV6   != (NETIF_F_TSO6 >> NETIF_F_GSO_SHIFT));
>  	BUILD_BUG_ON(SKB_GSO_FCOE    != (NETIF_F_FSO >> NETIF_F_GSO_SHIFT));
>  	BUILD_BUG_ON(SKB_GSO_GRE     != (NETIF_F_GSO_GRE >> NETIF_F_GSO_SHIFT));
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index ca8be45dd8be..cf95b325f9b4 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -674,7 +674,7 @@ enum {
>  	/* This indicates the tcp segment has CWR set. */
>  	SKB_GSO_TCP_ECN = 1 << 2,
>  
> -	SKB_GSO_TCP_FIXEDID = 1 << 3,
> +	__SKB_GSO_TCP_FIXEDID = 1 << 3,
>  
>  	SKB_GSO_TCPV6 = 1 << 4,
>  
> @@ -707,6 +707,10 @@ enum {
>  	SKB_GSO_FRAGLIST = 1 << 18,
>  
>  	SKB_GSO_TCP_ACCECN = 1 << 19,
> +
> +	/* These don't correspond with netdev features. */

Can use clarification. Something like

    /* These indirectly together map onto the same netdev feature:
     * If NETIF_F_TSO_MANGLE is set it may mangle both inner and outer.
     */
> +	SKB_GSO_TCP_FIXEDID = 1 << 30,
> +	SKB_GSO_TCP_FIXEDID_INNER = 1 << 31,
>  };
>  
>  #if BITS_PER_LONG > 32
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 93a25d87b86b..f57c8dbf307f 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -3769,7 +3769,9 @@ static netdev_features_t gso_features_check(const struct sk_buff *skb,
>  		features &= ~dev->gso_partial_features;
>  
>  	/* Make sure to clear the IPv4 ID mangling feature if the
> -	 * IPv4 header has the potential to be fragmented.
> +	 * IPv4 header has the potential to be fragmented. For
> +	 * encapsulated packets, the outer headers are guaranteed to
> +	 * have incrementing IDs if DF is not set.

This is saying that if !DF then both inner and outer must be
incrementing?

Maybe the outer headers are [also] garuanteed to have incrementing IDs.

>  	 */
>  	if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4) {
>  		struct iphdr *iph = skb->encapsulation ?
> diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
> index 76e38092cd8a..fc7a6955fa0a 100644
> --- a/net/ipv4/af_inet.c
> +++ b/net/ipv4/af_inet.c
> @@ -1393,14 +1393,13 @@ struct sk_buff *inet_gso_segment(struct sk_buff *skb,
>  
>  	segs = ERR_PTR(-EPROTONOSUPPORT);
>  
> -	if (!skb->encapsulation || encap) {
> -		udpfrag = !!(skb_shinfo(skb)->gso_type & SKB_GSO_UDP);
> -		fixedid = !!(skb_shinfo(skb)->gso_type & SKB_GSO_TCP_FIXEDID);
> +	/* fixed ID is invalid if DF bit is not set */
> +	fixedid = !!(skb_shinfo(skb)->gso_type & (SKB_GSO_TCP_FIXEDID << encap));
> +	if (fixedid && !(ip_hdr(skb)->frag_off & htons(IP_DF)))
> +		goto out;
>  
> -		/* fixed ID is invalid if DF bit is not set */
> -		if (fixedid && !(ip_hdr(skb)->frag_off & htons(IP_DF)))
> -			goto out;
> -	}
> +	if (!skb->encapsulation || encap)
> +		udpfrag = !!(skb_shinfo(skb)->gso_type & SKB_GSO_UDP);
>  
>  	ops = rcu_dereference(inet_offloads[proto]);
>  	if (likely(ops && ops->callbacks.gso_segment)) {
> diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
> index 1949eede9ec9..e6612bd84d09 100644
> --- a/net/ipv4/tcp_offload.c
> +++ b/net/ipv4/tcp_offload.c
> @@ -471,7 +471,6 @@ INDIRECT_CALLABLE_SCOPE int tcp4_gro_complete(struct sk_buff *skb, int thoff)
>  	const u16 offset = NAPI_GRO_CB(skb)->network_offsets[skb->encapsulation];
>  	const struct iphdr *iph = (struct iphdr *)(skb->data + offset);
>  	struct tcphdr *th = tcp_hdr(skb);
> -	bool is_fixedid;
>  
>  	if (unlikely(NAPI_GRO_CB(skb)->is_flist)) {
>  		skb_shinfo(skb)->gso_type |= SKB_GSO_FRAGLIST | SKB_GSO_TCPV4;
> @@ -485,10 +484,8 @@ INDIRECT_CALLABLE_SCOPE int tcp4_gro_complete(struct sk_buff *skb, int thoff)
>  	th->check = ~tcp_v4_check(skb->len - thoff, iph->saddr,
>  				  iph->daddr, 0);
>  
> -	is_fixedid = (NAPI_GRO_CB(skb)->ip_fixedid >> skb->encapsulation) & 1;
> -
>  	skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV4 |
> -			(is_fixedid * SKB_GSO_TCP_FIXEDID);
> +			(NAPI_GRO_CB(skb)->ip_fixedid * SKB_GSO_TCP_FIXEDID);

This was only just introduced. And is still needed?

Re: [PATCH net-next v4 4/5] net: gro: remove unnecessary df checks

[Willem de Bruijn]

Richard Gobert wrote:
> Currently, packets with fixed IDs will be merged only if their
> don't-fragment bit is set. Merged packets are re-split into segments
> before being fragmented, so the result is the same as if the packets
> weren't merged to begin with.

This can perhaps be reworded a bit for clarity. Something like "With
the changes in the earlier patches in this series, the ID state (fixed
or incrementing) is now recorded for both inner and outer IPv4 headers,
so the restriction to only coalesce packets with fixed IDs can now be
lifted."
> 
> Remove unnecessary don't-fragment checks.
> 
> Signed-off-by: Richard Gobert <richardbgobert@gmail.com>
> ---
>  include/net/gro.h                 | 5 ++---
>  net/ipv4/af_inet.c                | 3 ---
>  tools/testing/selftests/net/gro.c | 9 ++++-----
>  3 files changed, 6 insertions(+), 11 deletions(-)
> 
> diff --git a/include/net/gro.h b/include/net/gro.h
> index 322c5517f508..691f267b3969 100644
> --- a/include/net/gro.h
> +++ b/include/net/gro.h
> @@ -448,17 +448,16 @@ static inline int inet_gro_flush(const struct iphdr *iph, const struct iphdr *ip
>  	const u32 id2 = ntohl(*(__be32 *)&iph2->id);
>  	const u16 ipid_offset = (id >> 16) - (id2 >> 16);
>  	const u16 count = NAPI_GRO_CB(p)->count;
> -	const u32 df = id & IP_DF;
>  
>  	/* All fields must match except length and checksum. */
> -	if ((iph->ttl ^ iph2->ttl) | (iph->tos ^ iph2->tos) | (df ^ (id2 & IP_DF)))
> +	if ((iph->ttl ^ iph2->ttl) | (iph->tos ^ iph2->tos) | ((id ^ id2) & IP_DF))
>  		return true;

This is just a cleanup?

If so, please make a brief note in the commit message. I end up
staring whether there is some deeper meaning relevant to the
functional change.

>  
>  	/* When we receive our second frame we can make a decision on if we
>  	 * continue this flow as an atomic flow with a fixed ID or if we use
>  	 * an incrementing ID.
>  	 */
> -	if (count == 1 && df && !ipid_offset)
> +	if (count == 1 && !ipid_offset)
>  		NAPI_GRO_CB(p)->ip_fixedid |= 1 << inner;
>  
>  	return ipid_offset ^ (count * !(NAPI_GRO_CB(p)->ip_fixedid & (1 << inner)));
> diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
> index fc7a6955fa0a..c0542d9187e2 100644
> --- a/net/ipv4/af_inet.c
> +++ b/net/ipv4/af_inet.c
> @@ -1393,10 +1393,7 @@ struct sk_buff *inet_gso_segment(struct sk_buff *skb,
>  
>  	segs = ERR_PTR(-EPROTONOSUPPORT);
>  
> -	/* fixed ID is invalid if DF bit is not set */
>  	fixedid = !!(skb_shinfo(skb)->gso_type & (SKB_GSO_TCP_FIXEDID << encap));
> -	if (fixedid && !(ip_hdr(skb)->frag_off & htons(IP_DF)))
> -		goto out;

I understand why the GRO constraint can now be relaxed. But why does
this also affect GSO?

Fixed ID is invalid on the wire if DF is not set. Is the idea behind
this change that GRO + GSO is just forwarding existing packets. Even
if the incoming packets were invalid on this point?

>  
>  	if (!skb->encapsulation || encap)
>  		udpfrag = !!(skb_shinfo(skb)->gso_type & SKB_GSO_UDP);
> diff --git a/tools/testing/selftests/net/gro.c b/tools/testing/selftests/net/gro.c
> index d5824eadea10..3d4a82a2607c 100644
> --- a/tools/testing/selftests/net/gro.c
> +++ b/tools/testing/selftests/net/gro.c
> @@ -670,7 +670,7 @@ static void send_flush_id_case(int fd, struct sockaddr_ll *daddr, int tcase)
>  		iph2->id = htons(9);
>  		break;
>  
> -	case 3: /* DF=0, Fixed - should not coalesce */
> +	case 3: /* DF=0, Fixed - should coalesce */
>  		iph1->frag_off &= ~htons(IP_DF);
>  		iph1->id = htons(8);
>  
> @@ -1188,10 +1188,9 @@ static void gro_receiver(void)
>  			correct_payload[0] = PAYLOAD_LEN * 2;
>  			check_recv_pkts(rxfd, correct_payload, 1);
>  
> -			printf("DF=0, Fixed - should not coalesce: ");
> -			correct_payload[0] = PAYLOAD_LEN;
> -			correct_payload[1] = PAYLOAD_LEN;
> -			check_recv_pkts(rxfd, correct_payload, 2);
> +			printf("DF=0, Fixed - should coalesce: ");
> +			correct_payload[0] = PAYLOAD_LEN * 2;
> +			check_recv_pkts(rxfd, correct_payload, 1);
>  
>  			printf("DF=1, 2 Incrementing and one fixed - should coalesce only first 2 packets: ");
>  			correct_payload[0] = PAYLOAD_LEN * 2;
> -- 
> 2.36.1
> 

Re: [PATCH net-next v4 5/5] selftests/net: test ipip packets in gro.sh

[Willem de Bruijn]

Richard Gobert wrote:
> Add IPIP test-cases to the GRO selftest.
> 
> This selftest already contains IP ID test-cases. They are now
> also tested for encapsulated packets.
> 
> This commit also fixes ipip packet generation in the test.
> 
> Signed-off-by: Richard Gobert <richardbgobert@gmail.com>
> ---
>  tools/testing/selftests/net/gro.c  | 49 ++++++++++++++++++++++++------
>  tools/testing/selftests/net/gro.sh |  5 +--
>  2 files changed, 42 insertions(+), 12 deletions(-)
> 
> diff --git a/tools/testing/selftests/net/gro.c b/tools/testing/selftests/net/gro.c
> index 3d4a82a2607c..451dc1c1eac5 100644
> --- a/tools/testing/selftests/net/gro.c
> +++ b/tools/testing/selftests/net/gro.c
> @@ -93,6 +93,7 @@ static bool tx_socket = true;
>  static int tcp_offset = -1;
>  static int total_hdr_len = -1;
>  static int ethhdr_proto = -1;
> +static bool ipip;
>  static const int num_flush_id_cases = 6;
>  
>  static void vlog(const char *fmt, ...)
> @@ -114,7 +115,9 @@ static void setup_sock_filter(int fd)
>  	int ipproto_off, opt_ipproto_off;
>  	int next_off;
>  
> -	if (proto == PF_INET)
> +	if (ipip)
> +		next_off = sizeof(struct iphdr) + offsetof(struct iphdr, protocol);
> +	else if (proto == PF_INET)
>  		next_off = offsetof(struct iphdr, protocol);
>  	else
>  		next_off = offsetof(struct ipv6hdr, nexthdr);
> @@ -244,7 +247,7 @@ static void fill_datalinklayer(void *buf)
>  	eth->h_proto = ethhdr_proto;
>  }
>  
> -static void fill_networklayer(void *buf, int payload_len)
> +static void fill_networklayer(void *buf, int payload_len, int protocol)
>  {
>  	struct ipv6hdr *ip6h = buf;
>  	struct iphdr *iph = buf;
> @@ -254,7 +257,7 @@ static void fill_networklayer(void *buf, int payload_len)
>  
>  		ip6h->version = 6;
>  		ip6h->payload_len = htons(sizeof(struct tcphdr) + payload_len);
> -		ip6h->nexthdr = IPPROTO_TCP;
> +		ip6h->nexthdr = protocol;
>  		ip6h->hop_limit = 8;
>  		if (inet_pton(AF_INET6, addr6_src, &ip6h->saddr) != 1)
>  			error(1, errno, "inet_pton source ip6");
> @@ -266,7 +269,7 @@ static void fill_networklayer(void *buf, int payload_len)
>  		iph->version = 4;
>  		iph->ihl = 5;
>  		iph->ttl = 8;
> -		iph->protocol	= IPPROTO_TCP;
> +		iph->protocol	= protocol;
>  		iph->tot_len = htons(sizeof(struct tcphdr) +
>  				payload_len + sizeof(struct iphdr));
>  		iph->frag_off = htons(0x4000); /* DF = 1, MF = 0 */
> @@ -313,9 +316,19 @@ static void create_packet(void *buf, int seq_offset, int ack_offset,
>  {
>  	memset(buf, 0, total_hdr_len);
>  	memset(buf + total_hdr_len, 'a', payload_len);
> +
>  	fill_transportlayer(buf + tcp_offset, seq_offset, ack_offset,
>  			    payload_len, fin);
> -	fill_networklayer(buf + ETH_HLEN, payload_len);
> +
> +	if (ipip) {
> +		fill_networklayer(buf + ETH_HLEN + sizeof(struct iphdr),
> +				  payload_len, IPPROTO_TCP);
> +		fill_networklayer(buf + ETH_HLEN, payload_len + sizeof(struct iphdr),
> +				  IPPROTO_IPIP);

if respinning, minor request to insert in the order of the headers,
so IPIP first.

> +	} else {
> +		fill_networklayer(buf + ETH_HLEN, payload_len, IPPROTO_TCP);
> +	}
> +
>  	fill_datalinklayer(buf);
>  }
>  

> diff --git a/tools/testing/selftests/net/gro.sh b/tools/testing/selftests/net/gro.sh
> index 9e3f186bc2a1..d16ec365b3cf 100755
> --- a/tools/testing/selftests/net/gro.sh
> +++ b/tools/testing/selftests/net/gro.sh
> @@ -4,7 +4,7 @@
>  readonly SERVER_MAC="aa:00:00:00:00:02"
>  readonly CLIENT_MAC="aa:00:00:00:00:01"
>  readonly TESTS=("data" "ack" "flags" "tcp" "ip" "large")
> -readonly PROTOS=("ipv4" "ipv6")
> +readonly PROTOS=("ipv4" "ipv6" "ipip")
>  dev=""
>  test="all"
>  proto="ipv4"
> @@ -31,7 +31,8 @@ run_test() {
>        1>>log.txt
>      wait "${server_pid}"
>      exit_code=$?
> -    if [[ ${test} == "large" && -n "${KSFT_MACHINE_SLOW}" && \
> +    if [[ ( ${test} == "large" || ${protocol} == "ipip" ) && \
> +          -n "${KSFT_MACHINE_SLOW}" && \
>            ${exit_code} -ne 0 ]]; then
>          echo "Ignoring errors due to slow environment" 1>&2
>          exit_code=0

If you can no longer reproduce the need for this, and we see no
reason analytically why ipip would be more flaky than ipv4, then
please drop this. Else some future time we'll be scratching our heads
why this is here but will be afraid to touch it.