diff mbox series

[2/5] batman-adv: Don't increase MTU when set by user

Message ID 20230816163318.189996-3-sw@simonwunderlich.de (mailing list archive)
State Accepted
Commit d8e42a2b0addf238be8b3b37dcd9795a5c1be459
Delegated to: Netdev Maintainers
Headers show
Series [1/5] batman-adv: Trigger events for auto adjusted MTU | expand

Checks

Context Check Description
netdev/series_format warning Pull request is its own cover letter; Target tree name not specified in the subject
netdev/tree_selection success Guessed tree name to be net-next
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 1330 this patch: 1330
netdev/cc_maintainers warning 4 maintainers not CCed: edumazet@google.com a@unstable.cc mareklindner@neomailbox.ch pabeni@redhat.com
netdev/build_clang success Errors and warnings before: 1353 this patch: 1353
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success Fixes tag looks correct
netdev/build_allmodconfig_warn success Errors and warnings before: 1353 this patch: 1353
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 46 lines checked
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

Simon Wunderlich Aug. 16, 2023, 4:33 p.m. UTC 
From: Sven Eckelmann <sven@narfation.org>

If the user set an MTU value, it usually means that there are special
requirements for the MTU. But if an interface gots activated, the MTU was
always recalculated and then the user set value was overwritten.

The only reason why this user set value has to be overwritten, is when the
MTU has to be decreased because batman-adv is not able to transfer packets
with the user specified size.

Fixes: c6c8fea29769 ("net: Add batman-adv meshing protocol")
Cc: stable@vger.kernel.org
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
---
 net/batman-adv/hard-interface.c | 14 +++++++++++++-
 net/batman-adv/soft-interface.c |  3 +++
 net/batman-adv/types.h          |  6 ++++++
 3 files changed, 22 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c
index ae5762af0146..24c9c0c3f316 100644
--- a/net/batman-adv/hard-interface.c
+++ b/net/batman-adv/hard-interface.c
@@ -630,7 +630,19 @@  int batadv_hardif_min_mtu(struct net_device *soft_iface)
  */
 void batadv_update_min_mtu(struct net_device *soft_iface)
 {
-	dev_set_mtu(soft_iface, batadv_hardif_min_mtu(soft_iface));
+	struct batadv_priv *bat_priv = netdev_priv(soft_iface);
+	int limit_mtu;
+	int mtu;
+
+	mtu = batadv_hardif_min_mtu(soft_iface);
+
+	if (bat_priv->mtu_set_by_user)
+		limit_mtu = bat_priv->mtu_set_by_user;
+	else
+		limit_mtu = ETH_DATA_LEN;
+
+	mtu = min(mtu, limit_mtu);
+	dev_set_mtu(soft_iface, mtu);
 
 	/* Check if the local translate table should be cleaned up to match a
 	 * new (and smaller) MTU.
diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c
index d3fdf82282af..85d00dc9ce32 100644
--- a/net/batman-adv/soft-interface.c
+++ b/net/batman-adv/soft-interface.c
@@ -153,11 +153,14 @@  static int batadv_interface_set_mac_addr(struct net_device *dev, void *p)
 
 static int batadv_interface_change_mtu(struct net_device *dev, int new_mtu)
 {
+	struct batadv_priv *bat_priv = netdev_priv(dev);
+
 	/* check ranges */
 	if (new_mtu < 68 || new_mtu > batadv_hardif_min_mtu(dev))
 		return -EINVAL;
 
 	dev->mtu = new_mtu;
+	bat_priv->mtu_set_by_user = new_mtu;
 
 	return 0;
 }
diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h
index ca9449ec9836..cf1a0eafe3ab 100644
--- a/net/batman-adv/types.h
+++ b/net/batman-adv/types.h
@@ -1546,6 +1546,12 @@  struct batadv_priv {
 	/** @soft_iface: net device which holds this struct as private data */
 	struct net_device *soft_iface;
 
+	/**
+	 * @mtu_set_by_user: MTU was set once by user
+	 * protected by rtnl_lock
+	 */
+	int mtu_set_by_user;
+
 	/**
 	 * @bat_counters: mesh internal traffic statistic counters (see
 	 *  batadv_counters)