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Message-ID: <CANn89iL11WjtqNx0=fL2hOzpH_S6y=J5U9uS3g+iusupJLLsTg@mail.gmail.com>
Date: Fri, 27 Jan 2023 18:41:26 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: Xin Long <lucien.xin@...il.com>
Cc: network dev <netdev@...r.kernel.org>, davem@...emloft.net,
kuba@...nel.org, Paolo Abeni <pabeni@...hat.com>,
David Ahern <dsahern@...il.com>,
Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
Pravin B Shelar <pshelar@....org>,
Jamal Hadi Salim <jhs@...atatu.com>,
Cong Wang <xiyou.wangcong@...il.com>,
Jiri Pirko <jiri@...nulli.us>,
Pablo Neira Ayuso <pablo@...filter.org>,
Florian Westphal <fw@...len.de>,
Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
Ilya Maximets <i.maximets@....org>,
Aaron Conole <aconole@...hat.com>,
Roopa Prabhu <roopa@...dia.com>,
Nikolay Aleksandrov <razor@...ckwall.org>,
Mahesh Bandewar <maheshb@...gle.com>,
Paul Moore <paul@...l-moore.com>,
Guillaume Nault <gnault@...hat.com>
Subject: Re: [PATCHv3 net-next 10/10] net: add support for ipv4 big tcp
On Fri, Jan 27, 2023 at 5:00 PM Xin Long <lucien.xin@...il.com> wrote:
>
> Similar to Eric's IPv6 BIG TCP, this patch is to enable IPv4 BIG TCP.
>
> Firstly, allow sk->sk_gso_max_size to be set to a value greater than
> GSO_LEGACY_MAX_SIZE by not trimming gso_max_size in sk_trim_gso_size()
> for IPv4 TCP sockets.
>
> Then on TX path, set IP header tot_len to 0 when skb->len > IP_MAX_MTU
> in __ip_local_out() to allow to send BIG TCP packets, and this implies
> that skb->len is the length of a IPv4 packet; On RX path, use skb->len
> as the length of the IPv4 packet when the IP header tot_len is 0 and
> skb->len > IP_MAX_MTU in ip_rcv_core(). As the API iph_set_totlen() and
> skb_ip_totlen() are used in __ip_local_out() and ip_rcv_core(), we only
> need to update these APIs.
>
> Also in GRO receive, add the check for ETH_P_IP/IPPROTO_TCP, and allows
> the merged packet size >= GRO_LEGACY_MAX_SIZE in skb_gro_receive(). In
> GRO complete, set IP header tot_len to 0 when the merged packet size
> greater than IP_MAX_MTU in iph_set_totlen() so that it can be processed
> on RX path.
>
> Note that by checking skb_is_gso_tcp() in API iph_totlen(), it makes
> this implementation safe to use iph->len == 0 indicates IPv4 BIG TCP
> packets.
>
> Signed-off-by: Xin Long <lucien.xin@...il.com>
> ---
> net/core/gro.c | 12 +++++++-----
> net/core/sock.c | 8 ++++++--
> net/ipv4/af_inet.c | 7 ++++---
> net/ipv4/ip_input.c | 2 +-
> net/ipv4/ip_output.c | 2 +-
> 5 files changed, 19 insertions(+), 12 deletions(-)
>
> diff --git a/net/core/gro.c b/net/core/gro.c
> index 506f83d715f8..b15f85546bdd 100644
> --- a/net/core/gro.c
> +++ b/net/core/gro.c
> @@ -162,16 +162,18 @@ int skb_gro_receive(struct sk_buff *p, struct sk_buff *skb)
> struct sk_buff *lp;
> int segs;
>
> - /* pairs with WRITE_ONCE() in netif_set_gro_max_size() */
> - gro_max_size = READ_ONCE(p->dev->gro_max_size);
> + /* pairs with WRITE_ONCE() in netif_set_gro(_ipv4)_max_size() */
> + gro_max_size = p->protocol == htons(ETH_P_IPV6) ?
> + READ_ONCE(p->dev->gro_max_size) :
> + READ_ONCE(p->dev->gro_ipv4_max_size);
>
> if (unlikely(p->len + len >= gro_max_size || NAPI_GRO_CB(skb)->flush))
> return -E2BIG;
>
> if (unlikely(p->len + len >= GRO_LEGACY_MAX_SIZE)) {
> - if (p->protocol != htons(ETH_P_IPV6) ||
> - skb_headroom(p) < sizeof(struct hop_jumbo_hdr) ||
> - ipv6_hdr(p)->nexthdr != IPPROTO_TCP ||
> + if (NAPI_GRO_CB(skb)->proto != IPPROTO_TCP ||
> + (p->protocol == htons(ETH_P_IPV6) &&
> + skb_headroom(p) < sizeof(struct hop_jumbo_hdr)) ||
> p->encapsulation)
> return -E2BIG;
> }
> diff --git a/net/core/sock.c b/net/core/sock.c
> index 7ba4891460ad..c98f9a4eeff9 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -2383,6 +2383,8 @@ static void sk_trim_gso_size(struct sock *sk)
> !ipv6_addr_v4mapped(&sk->sk_v6_rcv_saddr))
> return;
> #endif
> + if (sk->sk_family == AF_INET && sk_is_tcp(sk))
> + return;
Or simply
diff --git a/net/core/sock.c b/net/core/sock.c
index 7ba4891460adbd6c13c0ce1dcdd7f23c8c1f0f5d..dcb8fff91fd9a9472267a2cf2fdc98114a7d2b7d
100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2375,14 +2375,9 @@ EXPORT_SYMBOL_GPL(sk_free_unlock_clone);
static void sk_trim_gso_size(struct sock *sk)
{
- if (sk->sk_gso_max_size <= GSO_LEGACY_MAX_SIZE)
+ if (sk->sk_gso_max_size <= GSO_LEGACY_MAX_SIZE ||
+ sk_is_tcp(sk))
return;
-#if IS_ENABLED(CONFIG_IPV6)
- if (sk->sk_family == AF_INET6 &&
- sk_is_tcp(sk) &&
- !ipv6_addr_v4mapped(&sk->sk_v6_rcv_saddr))
- return;
-#endif
sk->sk_gso_max_size = GSO_LEGACY_MAX_SIZE;
}
> sk->sk_gso_max_size = GSO_LEGACY_MAX_SIZE;
> }
>
> @@ -2403,8 +2405,10 @@ void sk_setup_caps(struct sock *sk, struct dst_entry *dst)
> sk->sk_route_caps &= ~NETIF_F_GSO_MASK;
> } else {
> sk->sk_route_caps |= NETIF_F_SG | NETIF_F_HW_CSUM;
> - /* pairs with the WRITE_ONCE() in netif_set_gso_max_size() */
> - sk->sk_gso_max_size = READ_ONCE(dst->dev->gso_max_size);
> + /* pairs with the WRITE_ONCE() in netif_set_gso(_ipv4)_max_size() */
> + sk->sk_gso_max_size = sk->sk_family == AF_INET6 ?
> + READ_ONCE(dst->dev->gso_max_size) :
> + READ_ONCE(dst->dev->gso_ipv4_max_size);
> sk_trim_gso_size(sk);
> sk->sk_gso_max_size -= (MAX_TCP_HEADER + 1);
> /* pairs with the WRITE_ONCE() in netif_set_gso_max_segs() */
> diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
> index 6c0ec2789943..2f992a323b95 100644
> --- a/net/ipv4/af_inet.c
> +++ b/net/ipv4/af_inet.c
> @@ -1485,6 +1485,7 @@ struct sk_buff *inet_gro_receive(struct list_head *head, struct sk_buff *skb)
> if (unlikely(ip_fast_csum((u8 *)iph, 5)))
> goto out;
>
> + NAPI_GRO_CB(skb)->proto = proto;
> id = ntohl(*(__be32 *)&iph->id);
> flush = (u16)((ntohl(*(__be32 *)iph) ^ skb_gro_len(skb)) | (id & ~IP_DF));
> id >>= 16;
> @@ -1618,9 +1619,9 @@ int inet_recv_error(struct sock *sk, struct msghdr *msg, int len, int *addr_len)
>
> int inet_gro_complete(struct sk_buff *skb, int nhoff)
> {
> - __be16 newlen = htons(skb->len - nhoff);
> struct iphdr *iph = (struct iphdr *)(skb->data + nhoff);
> const struct net_offload *ops;
> + __be16 totlen = iph->tot_len;
> int proto = iph->protocol;
> int err = -ENOSYS;
>
> @@ -1629,8 +1630,8 @@ int inet_gro_complete(struct sk_buff *skb, int nhoff)
> skb_set_inner_network_header(skb, nhoff);
> }
>
> - csum_replace2(&iph->check, iph->tot_len, newlen);
> - iph->tot_len = newlen;
> + iph_set_totlen(iph, skb->len - nhoff);
> + csum_replace2(&iph->check, totlen, iph->tot_len);
>
> ops = rcu_dereference(inet_offloads[proto]);
> if (WARN_ON(!ops || !ops->callbacks.gro_complete))
> diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c
> index e880ce77322a..0aa8c49b4e1b 100644
> --- a/net/ipv4/ip_input.c
> +++ b/net/ipv4/ip_input.c
> @@ -511,7 +511,7 @@ static struct sk_buff *ip_rcv_core(struct sk_buff *skb, struct net *net)
> if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl)))
> goto csum_error;
>
> - len = ntohs(iph->tot_len);
> + len = skb_ip_totlen(skb);
len = iph_totlen(skb, iph);
> if (skb->len < len) {
> drop_reason = SKB_DROP_REASON_PKT_TOO_SMALL;
> __IP_INC_STATS(net, IPSTATS_MIB_INTRUNCATEDPKTS);
> diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
> index 922c87ef1ab5..4e4e308c3230 100644
> --- a/net/ipv4/ip_output.c
> +++ b/net/ipv4/ip_output.c
> @@ -100,7 +100,7 @@ int __ip_local_out(struct net *net, struct sock *sk, struct sk_buff *skb)
> {
> struct iphdr *iph = ip_hdr(skb);
>
> - iph->tot_len = htons(skb->len);
> + iph_set_totlen(iph, skb->len);
> ip_send_check(iph);
>
> /* if egress device is enslaved to an L3 master device pass the
> --
> 2.31.1
>
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