netdev - [PATCH v4 net-next 09/12] net: loopback: enable BIG TCP packets

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Message-Id: <20220506153048.3695721-10-eric.dumazet@gmail.com>
Date:   Fri,  6 May 2022 08:30:45 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     netdev <netdev@...r.kernel.org>, Coco Li <lixiaoyan@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH v4 net-next 09/12] net: loopback: enable BIG TCP packets

From: Eric Dumazet <edumazet@...gle.com>

Set the driver limit to 512 KB per TSO ipv6 packet.

This allows the admin/user to set a GSO ipv6 limit up to this value.

Tested:

ip link set dev lo gso_ipv6_max_size 200000
netperf -H ::1 -t TCP_RR -l 100 -- -r 80000,80000 &

tcpdump shows :

18:28:42.962116 IP6 ::1 > ::1: HBH 40051 > 63780: Flags [P.], seq 3626480001:3626560001, ack 3626560001, win 17743, options [nop,nop,TS val 3771179265 ecr 3771179265], length 80000
18:28:42.962138 IP6 ::1.63780 > ::1.40051: Flags [.], ack 3626560001, win 17743, options [nop,nop,TS val 3771179265 ecr 3771179265], length 0
18:28:42.962152 IP6 ::1 > ::1: HBH 63780 > 40051: Flags [P.], seq 3626560001:3626640001, ack 3626560001, win 17743, options [nop,nop,TS val 3771179265 ecr 3771179265], length 80000
18:28:42.962157 IP6 ::1.40051 > ::1.63780: Flags [.], ack 3626640001, win 17743, options [nop,nop,TS val 3771179265 ecr 3771179265], length 0
18:28:42.962180 IP6 ::1 > ::1: HBH 40051 > 63780: Flags [P.], seq 3626560001:3626640001, ack 3626640001, win 17743, options [nop,nop,TS val 3771179265 ecr 3771179265], length 80000
18:28:42.962214 IP6 ::1.63780 > ::1.40051: Flags [.], ack 3626640001, win 17743, options [nop,nop,TS val 3771179266 ecr 3771179265], length 0
18:28:42.962228 IP6 ::1 > ::1: HBH 63780 > 40051: Flags [P.], seq 3626640001:3626720001, ack 3626640001, win 17743, options [nop,nop,TS val 3771179266 ecr 3771179265], length 80000
18:28:42.962233 IP6 ::1.40051 > ::1.63780: Flags [.], ack 3626720001, win 17743, options [nop,nop,TS val 3771179266 ecr 3771179266], length 0

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 drivers/net/loopback.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/loopback.c b/drivers/net/loopback.c
index 720394c0639b20a2fd6262e4ee9d5813c02802f1..f504dd0817092d63f0e929500ec49cfdda562c4b 100644
--- a/drivers/net/loopback.c
+++ b/drivers/net/loopback.c
@@ -191,6 +191,8 @@ static void gen_lo_setup(struct net_device *dev,
 	dev->netdev_ops		= dev_ops;
 	dev->needs_free_netdev	= true;
 	dev->priv_destructor	= dev_destructor;
+
+	netif_set_tso_max_size(dev, 512 * 1024);
 }
 
 /* The loopback device is special. There is only one instance
-- 
2.36.0.512.ge40c2bad7a-goog