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Tue, 23 Sep 2025 01:29:24 -0700 (PDT) Message-ID: Date: Tue, 23 Sep 2025 10:29:14 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH net-next v6 3/5] net: gso: restore ids of outer ip headers correctly To: Willem de Bruijn , netdev@vger.kernel.org, pabeni@redhat.com, ecree.xilinx@gmail.com Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, horms@kernel.org, corbet@lwn.net, saeedm@nvidia.com, tariqt@nvidia.com, mbloch@nvidia.com, leon@kernel.org, dsahern@kernel.org, ncardwell@google.com, kuniyu@google.com, shuah@kernel.org, sdf@fomichev.me, aleksander.lobakin@intel.com, florian.fainelli@broadcom.com, alexander.duyck@gmail.com, linux-kernel@vger.kernel.org, linux-net-drivers@amd.com References: <20250916144841.4884-1-richardbgobert@gmail.com> <20250916144841.4884-4-richardbgobert@gmail.com> From: Richard Gobert In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Willem de Bruijn wrote: > 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 >> Reviewed-by: Edward Cree # for sfc >> --- >> .../networking/segmentation-offloads.rst | 22 ++++++++++++------- >> .../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 | 8 ++++++- >> net/core/dev.c | 8 +++++-- >> net/ipv4/af_inet.c | 13 +++++------ >> net/ipv4/tcp_offload.c | 5 +---- >> 8 files changed, 60 insertions(+), 30 deletions(-) >> >> diff --git a/Documentation/networking/segmentation-offloads.rst b/Documentation/networking/segmentation-offloads.rst >> index 085e8fab03fd..72f69b22b28c 100644 >> --- a/Documentation/networking/segmentation-offloads.rst >> +++ b/Documentation/networking/segmentation-offloads.rst >> @@ -43,10 +43,19 @@ also point to the TCP header of the packet. >> For IPv4 segmentation we support one of two types in terms of the IP ID. >> The default behavior is to increment the IP ID with every segment. If the >> 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. >> +ID and all segments will use the same IP ID. >> + >> +For encapsulated packets, SKB_GSO_TCP_FIXEDID refers only to the outer header. >> +SKB_GSO_TCP_FIXEDID_INNER can be used to specify the same for the inner header. >> +Any combination of these two GSO types is allowed. >> + >> +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. For encapsulated packets, >> +NETIF_F_TSO_MANGLEID is relevant for both outer and inner headers, unless the >> +DF bit is not set on the outer header, in which case the device driver must >> +guarantee that the IP ID field is incremented in the outer header with every >> +segment. >> >> >> UDP Fragmentation Offload >> @@ -124,10 +133,7 @@ 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..480f66e21132 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..03005757c060 100644 >> --- a/drivers/net/ethernet/sfc/ef100_tx.c >> +++ b/drivers/net/ethernet/sfc/ef100_tx.c >> @@ -189,6 +189,7 @@ 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_outer = ESE_GZ_TX_DESC_IP4_ID_INC_MOD16; >> u32 mangleid = ESE_GZ_TX_DESC_IP4_ID_INC_MOD16; >> unsigned int outer_ip_offset, outer_l4_offset; >> u16 vlan_tci = skb_vlan_tag_get(skb); >> @@ -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; > > Should this also remove the original features from the type. Given > that no NETIF_F equivalent exists for those. > This is already done with NETIF_F_GSO_MASK in the line below. >> + >> + 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..646fb66ba948 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 +707,12 @@ enum { >> SKB_GSO_FRAGLIST = 1 << 18, >> >> SKB_GSO_TCP_ACCECN = 1 << 19, >> + >> + /* These indirectly map onto the same netdev feature. >> + * If NETIF_F_TSO_MANGLEID is set it may mangle both inner and outer IDs. >> + */ >> + 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..6b34b3e857d4 100644 >> --- a/net/core/dev.c >> +++ b/net/core/dev.c >> @@ -3768,8 +3768,12 @@ static netdev_features_t gso_features_check(const struct sk_buff *skb, >> if (!(skb_shinfo(skb)->gso_type & SKB_GSO_PARTIAL)) >> features &= ~dev->gso_partial_features; >> >> - /* Make sure to clear the IPv4 ID mangling feature if the >> - * IPv4 header has the potential to be fragmented. >> + /* Make sure to clear the IPv4 ID mangling feature if the IPv4 header >> + * has the potential to be fragmented. For encapsulated packets, the ID >> + * mangling feature is guaranteed not to use the same ID for the outer >> + * IPv4 headers of the generated segments if the headers have the >> + * potential to be fragmented, so there is no need to clear the IPv4 ID >> + * mangling feature. > > If respinning: same comment from v5: please convert the assertion > that ID mangling is guaranteed to not to use the same ID for !DF > to an explanation: point to or copy the statement from the GSO > partial documentation. > I'll add a direct reference to the documentation and send v8 shortly. >> */ >> 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 >> > >