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From:   Angus Chen <angus.chen@jaguarmicro.com>
To:     davem@davemloft.net, dsahern@kernel.org, edumazet@google.com,
        kuba@kernel.org, pabeni@redhat.com
Cc:     netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        idosch@idosch.org, petrm@nvidia.com,
        Angus Chen <angus.chen@jaguarmicro.com>
Subject: [PATCH v3] net: Remove low_thresh in ip defrag
Date:   Wed, 17 May 2023 08:18:20 +0800
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As low_thresh has no work in fragment reassembles,mark it to be unused.
And Mark it deprecated in sysctl Document.

Signed-off-by: Angus Chen <angus.chen@jaguarmicro.com>
---

v2:
 Fix some spelling errors,and remove low_thresh from struct fqdir.
 suggested by Jakub Kicinski <kuba@kernel.org>.

v3:
  Change low_thresh to low_thresh_unused in struct fqdir.

 Documentation/networking/nf_conntrack-sysctl.rst |  1 +
 include/net/inet_frag.h                          |  5 ++++-
 net/ieee802154/6lowpan/reassembly.c              |  6 +++---
 net/ipv4/ip_fragment.c                           | 10 ++++------
 net/ipv6/netfilter/nf_conntrack_reasm.c          |  6 +++---
 net/ipv6/reassembly.c                            |  6 +++---
 6 files changed, 18 insertions(+), 16 deletions(-)

diff --git a/Documentation/networking/nf_conntrack-sysctl.rst b/Documentation/networking/nf_conntrack-sysctl.rst
index 8b1045c3b59e..9ca356bc7217 100644
--- a/Documentation/networking/nf_conntrack-sysctl.rst
+++ b/Documentation/networking/nf_conntrack-sysctl.rst
@@ -55,6 +55,7 @@ nf_conntrack_frag6_high_thresh - INTEGER
 	nf_conntrack_frag6_low_thresh is reached.
 
 nf_conntrack_frag6_low_thresh - INTEGER
+	(Obsolete since linux-4.17)
 	default 196608
 
 	See nf_conntrack_frag6_low_thresh
diff --git a/include/net/inet_frag.h b/include/net/inet_frag.h
index b23ddec3cd5c..6ef360e4b729 100644
--- a/include/net/inet_frag.h
+++ b/include/net/inet_frag.h
@@ -13,7 +13,10 @@
 struct fqdir {
 	/* sysctls */
 	long			high_thresh;
-	long			low_thresh;
+	/* low_thresh is unused since linux-4.17,
+	 * keep it just to avoid getting warning from ensure_safe_net_sysctl.
+	 */
+	long			low_thresh_unused;
 	int			timeout;
 	int			max_dist;
 	struct inet_frags	*f;
diff --git a/net/ieee802154/6lowpan/reassembly.c b/net/ieee802154/6lowpan/reassembly.c
index a91283d1e5bf..c46cbe001646 100644
--- a/net/ieee802154/6lowpan/reassembly.c
+++ b/net/ieee802154/6lowpan/reassembly.c
@@ -374,8 +374,8 @@ static int __net_init lowpan_frags_ns_sysctl_register(struct net *net)
 	}
 
 	table[0].data	= &ieee802154_lowpan->fqdir->high_thresh;
-	table[0].extra1	= &ieee802154_lowpan->fqdir->low_thresh;
-	table[1].data	= &ieee802154_lowpan->fqdir->low_thresh;
+	table[0].extra1	= &ieee802154_lowpan->fqdir->low_thresh_unused;
+	table[1].data	= &ieee802154_lowpan->fqdir->low_thresh_unused;
 	table[1].extra2	= &ieee802154_lowpan->fqdir->high_thresh;
 	table[2].data	= &ieee802154_lowpan->fqdir->timeout;
 
@@ -451,7 +451,7 @@ static int __net_init lowpan_frags_init_net(struct net *net)
 		return res;
 
 	ieee802154_lowpan->fqdir->high_thresh = IPV6_FRAG_HIGH_THRESH;
-	ieee802154_lowpan->fqdir->low_thresh = IPV6_FRAG_LOW_THRESH;
+	ieee802154_lowpan->fqdir->low_thresh_unused = IPV6_FRAG_LOW_THRESH;
 	ieee802154_lowpan->fqdir->timeout = IPV6_FRAG_TIMEOUT;
 
 	res = lowpan_frags_ns_sysctl_register(net);
diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index 69c00ffdcf3e..9d72673b048b 100644
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -609,8 +609,8 @@ static int __net_init ip4_frags_ns_ctl_register(struct net *net)
 
 	}
 	table[0].data	= &net->ipv4.fqdir->high_thresh;
-	table[0].extra1	= &net->ipv4.fqdir->low_thresh;
-	table[1].data	= &net->ipv4.fqdir->low_thresh;
+	table[0].extra1	= &net->ipv4.fqdir->low_thresh_unused;
+	table[1].data	= &net->ipv4.fqdir->low_thresh_unused;
 	table[1].extra2	= &net->ipv4.fqdir->high_thresh;
 	table[2].data	= &net->ipv4.fqdir->timeout;
 	table[3].data	= &net->ipv4.fqdir->max_dist;
@@ -674,12 +674,10 @@ static int __net_init ipv4_frags_init_net(struct net *net)
 	 * A 64K fragment consumes 129736 bytes (44*2944)+200
 	 * (1500 truesize == 2944, sizeof(struct ipq) == 200)
 	 *
-	 * We will commit 4MB at one time. Should we cross that limit
-	 * we will prune down to 3MB, making room for approx 8 big 64K
-	 * fragments 8x128k.
+	 * We will commit 4MB at one time. And mark low_thresh be unused.
 	 */
 	net->ipv4.fqdir->high_thresh = 4 * 1024 * 1024;
-	net->ipv4.fqdir->low_thresh  = 3 * 1024 * 1024;
+	net->ipv4.fqdir->low_thresh_unused  = 3 * 1024 * 1024;
 	/*
 	 * Important NOTE! Fragment queue must be destroyed before MSL expires.
 	 * RFC791 is wrong proposing to prolongate timer each fragment arrival
diff --git a/net/ipv6/netfilter/nf_conntrack_reasm.c b/net/ipv6/netfilter/nf_conntrack_reasm.c
index d13240f13607..013f16ecdcd1 100644
--- a/net/ipv6/netfilter/nf_conntrack_reasm.c
+++ b/net/ipv6/netfilter/nf_conntrack_reasm.c
@@ -82,10 +82,10 @@ static int nf_ct_frag6_sysctl_register(struct net *net)
 	nf_frag = nf_frag_pernet(net);
 
 	table[0].data	= &nf_frag->fqdir->timeout;
-	table[1].data	= &nf_frag->fqdir->low_thresh;
+	table[1].data	= &nf_frag->fqdir->low_thresh_unused;
 	table[1].extra2	= &nf_frag->fqdir->high_thresh;
 	table[2].data	= &nf_frag->fqdir->high_thresh;
-	table[2].extra1	= &nf_frag->fqdir->low_thresh;
+	table[2].extra1	= &nf_frag->fqdir->low_thresh_unused;
 
 	hdr = register_net_sysctl(net, "net/netfilter", table);
 	if (hdr == NULL)
@@ -500,7 +500,7 @@ static int nf_ct_net_init(struct net *net)
 		return res;
 
 	nf_frag->fqdir->high_thresh = IPV6_FRAG_HIGH_THRESH;
-	nf_frag->fqdir->low_thresh = IPV6_FRAG_LOW_THRESH;
+	nf_frag->fqdir->low_thresh_unused = IPV6_FRAG_LOW_THRESH;
 	nf_frag->fqdir->timeout = IPV6_FRAG_TIMEOUT;
 
 	res = nf_ct_frag6_sysctl_register(net);
diff --git a/net/ipv6/reassembly.c b/net/ipv6/reassembly.c
index 5bc8a28e67f9..59b3fc8d9e6b 100644
--- a/net/ipv6/reassembly.c
+++ b/net/ipv6/reassembly.c
@@ -465,8 +465,8 @@ static int __net_init ip6_frags_ns_sysctl_register(struct net *net)
 
 	}
 	table[0].data	= &net->ipv6.fqdir->high_thresh;
-	table[0].extra1	= &net->ipv6.fqdir->low_thresh;
-	table[1].data	= &net->ipv6.fqdir->low_thresh;
+	table[0].extra1	= &net->ipv6.fqdir->low_thresh_unused;
+	table[1].data	= &net->ipv6.fqdir->low_thresh_unused;
 	table[1].extra2	= &net->ipv6.fqdir->high_thresh;
 	table[2].data	= &net->ipv6.fqdir->timeout;
 
@@ -536,7 +536,7 @@ static int __net_init ipv6_frags_init_net(struct net *net)
 		return res;
 
 	net->ipv6.fqdir->high_thresh = IPV6_FRAG_HIGH_THRESH;
-	net->ipv6.fqdir->low_thresh = IPV6_FRAG_LOW_THRESH;
+	net->ipv6.fqdir->low_thresh_unused = IPV6_FRAG_LOW_THRESH;
 	net->ipv6.fqdir->timeout = IPV6_FRAG_TIMEOUT;
 
 	res = ip6_frags_ns_sysctl_register(net);
-- 
2.25.1