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Mon, 15 Sep 2025 01:47:07 -0700 (PDT) Message-ID: Date: Mon, 15 Sep 2025 10:46:57 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH net-next v4 2/5] net: gro: only merge packets with incrementing or fixed outer ids To: Willem de Bruijn , netdev@vger.kernel.org Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, corbet@lwn.net, saeedm@nvidia.com, tariqt@nvidia.com, mbloch@nvidia.com, leon@kernel.org, ecree.xilinx@gmail.com, 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: <20250901113826.6508-1-richardbgobert@gmail.com> <20250901113826.6508-3-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: >> 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 >> --- >> 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. > Yes, I noticed this when working on this change and there is no good reason not to do this for UDP as well. I think we should address this in a separate patch series. >> >> tcp_gro_complete(skb); >> return 0; >> -- >> 2.36.1 >> > >