From: Subash Abhinov Kasiviswanathan <subash.a.kasiviswanathan@oss.qualcomm.com>
To: davem@davemloft.net, edumazet@google.com, kuba@kernel.org,
pabeni@redhat.com, andrew+netdev@lunn.ch, corbet@lwn.net
Cc: horms@kernel.org, skhan@linuxfoundation.org,
rdunlap@infradead.org, netdev@vger.kernel.org,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
Subash Abhinov Kasiviswanathan
<subash.a.kasiviswanathan@oss.qualcomm.com>,
Sean Tranchetti <sean.tranchetti@oss.qualcomm.com>
Subject: [PATCH net-next v2 1/8] net: qualcomm: rmnet: Update MTU handling during format changes
Date: Wed, 7 Oct 2026 17:55:38 -0700 [thread overview]
Message-ID: <20261008005543.2630828-2-subash.a.kasiviswanathan@oss.qualcomm.com> (raw)
In-Reply-To: <20261008005543.2630828-1-subash.a.kasiviswanathan@oss.qualcomm.com>
Calculate the MTU headroom from the requested data format when creating
an rmnet device. Resize existing endpoint MTUs when a newlink or changelink
requests a format that requires a smaller MTU.
Pass the requested format through the MTU helpers so the first device and
existing devices use the same headroom calculation. Validate the target MTU
before resizing existing endpoints and publish the new shared data format
only after all MTUs have been updated.
Co-developed-by: Sean Tranchetti <sean.tranchetti@oss.qualcomm.com>
Signed-off-by: Sean Tranchetti <sean.tranchetti@oss.qualcomm.com>
Signed-off-by: Subash Abhinov Kasiviswanathan <subash.a.kasiviswanathan@oss.qualcomm.com>
---
v2:
- newly added patch in v2
- fixes the pre-existing issue about MTU handling with data format
updates as reported by Sashiko
.../ethernet/qualcomm/rmnet/rmnet_config.c | 55 +++++++++------
.../net/ethernet/qualcomm/rmnet/rmnet_vnd.c | 68 +++++++++++++------
.../net/ethernet/qualcomm/rmnet/rmnet_vnd.h | 4 +-
3 files changed, 81 insertions(+), 46 deletions(-)
diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c
index 61b04c6c0390..e5a6289b018a 100644
--- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c
+++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c
@@ -143,6 +143,14 @@ static int rmnet_newlink(struct net_device *dev,
return -ENODEV;
}
+ if (data[IFLA_RMNET_FLAGS]) {
+ struct ifla_rmnet_flags *flags;
+
+ flags = nla_data(data[IFLA_RMNET_FLAGS]);
+ data_format &= ~flags->mask;
+ data_format |= flags->flags & flags->mask;
+ }
+
ep = kzalloc_obj(*ep);
if (!ep)
return -ENOMEM;
@@ -154,7 +162,8 @@ static int rmnet_newlink(struct net_device *dev,
goto err0;
port = rmnet_get_port_rtnl(real_dev);
- err = rmnet_vnd_newlink(mux_id, dev, port, real_dev, ep, extack);
+ err = rmnet_vnd_newlink(mux_id, dev, port, real_dev, ep, extack,
+ data_format);
if (err)
goto err1;
@@ -162,24 +171,23 @@ static int rmnet_newlink(struct net_device *dev,
if (err < 0)
goto err2;
+ /* Update existing MTUs before publishing the shared data format. */
+ err = rmnet_vnd_update_dev_mtu(port, real_dev, data_format);
+ if (err)
+ goto err3;
+
port->rmnet_mode = mode;
port->rmnet_dev = dev;
hlist_add_head_rcu(&ep->hlnode, &port->muxed_ep[mux_id]);
- if (data[IFLA_RMNET_FLAGS]) {
- struct ifla_rmnet_flags *flags;
-
- flags = nla_data(data[IFLA_RMNET_FLAGS]);
- data_format &= ~flags->mask;
- data_format |= flags->flags & flags->mask;
- }
-
netdev_dbg(dev, "data format [0x%08X]\n", data_format);
WRITE_ONCE(port->data_format, data_format);
return 0;
+err3:
+ netdev_upper_dev_unlink(real_dev, dev);
err2:
unregister_netdevice(dev);
rmnet_vnd_dellink(mux_id, port, ep);
@@ -301,9 +309,13 @@ static int rmnet_changelink(struct net_device *dev, struct nlattr *tb[],
struct netlink_ext_ack *extack)
{
struct rmnet_priv *priv = netdev_priv(dev);
+ struct ifla_rmnet_flags *flags;
struct net_device *real_dev;
struct rmnet_port *port;
+ u32 old_data_format;
+ u32 data_format;
u16 mux_id;
+ int err;
if (!dev)
return -ENODEV;
@@ -320,6 +332,13 @@ static int rmnet_changelink(struct net_device *dev, struct nlattr *tb[],
port = rmnet_get_port_rtnl(real_dev);
+ if (data[IFLA_RMNET_FLAGS]) {
+ old_data_format = READ_ONCE(port->data_format);
+ flags = nla_data(data[IFLA_RMNET_FLAGS]);
+ data_format = old_data_format & ~flags->mask;
+ data_format |= flags->flags & flags->mask;
+ }
+
if (data[IFLA_RMNET_MUX_ID]) {
mux_id = nla_get_u16(data[IFLA_RMNET_MUX_ID]);
@@ -346,21 +365,13 @@ static int rmnet_changelink(struct net_device *dev, struct nlattr *tb[],
}
if (data[IFLA_RMNET_FLAGS]) {
- struct ifla_rmnet_flags *flags;
- u32 old_data_format;
- u32 data_format;
-
- old_data_format = port->data_format;
- flags = nla_data(data[IFLA_RMNET_FLAGS]);
- data_format = old_data_format & ~flags->mask;
- data_format |= flags->flags & flags->mask;
- WRITE_ONCE(port->data_format, data_format);
-
- if (rmnet_vnd_update_dev_mtu(port, real_dev)) {
- WRITE_ONCE(port->data_format, old_data_format);
+ err = rmnet_vnd_update_dev_mtu(port, real_dev, data_format);
+ if (err) {
NL_SET_ERR_MSG_MOD(extack, "Invalid MTU on real dev");
- return -EINVAL;
+ return err;
}
+
+ WRITE_ONCE(port->data_format, data_format);
}
return 0;
diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_vnd.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_vnd.c
index 5f921cddf82b..d23f74b0aa47 100644
--- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_vnd.c
+++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_vnd.c
@@ -66,27 +66,25 @@ static netdev_tx_t rmnet_vnd_start_xmit(struct sk_buff *skb,
return NETDEV_TX_OK;
}
-static int rmnet_vnd_headroom(struct rmnet_port *port)
+static int rmnet_vnd_headroom(u32 data_format)
{
u32 headroom;
headroom = sizeof(struct rmnet_map_header);
- if (port->data_format & RMNET_FLAGS_EGRESS_MAP_CKSUMV4)
+ if (data_format & RMNET_FLAGS_EGRESS_MAP_CKSUMV4)
headroom += sizeof(struct rmnet_map_ul_csum_header);
return headroom;
}
-static int rmnet_vnd_change_mtu(struct net_device *rmnet_dev, int new_mtu)
+static int rmnet_vnd_change_mtu_with_format(struct net_device *rmnet_dev,
+ int new_mtu, u32 data_format)
{
struct rmnet_priv *priv = netdev_priv(rmnet_dev);
- struct rmnet_port *port;
u32 headroom;
- port = rmnet_get_port_rtnl(priv->real_dev);
-
- headroom = rmnet_vnd_headroom(port);
+ headroom = rmnet_vnd_headroom(data_format);
if (new_mtu < 0 || new_mtu > RMNET_MAX_PACKET_SIZE ||
new_mtu > (priv->real_dev->mtu - headroom))
@@ -96,6 +94,17 @@ static int rmnet_vnd_change_mtu(struct net_device *rmnet_dev, int new_mtu)
return 0;
}
+static int rmnet_vnd_change_mtu(struct net_device *rmnet_dev, int new_mtu)
+{
+ struct rmnet_priv *priv = netdev_priv(rmnet_dev);
+ struct rmnet_port *port;
+
+ port = rmnet_get_port_rtnl(priv->real_dev);
+
+ return rmnet_vnd_change_mtu_with_format(rmnet_dev, new_mtu,
+ READ_ONCE(port->data_format));
+}
+
static int rmnet_vnd_get_iflink(const struct net_device *dev)
{
struct rmnet_priv *priv = netdev_priv(dev);
@@ -308,8 +317,7 @@ int rmnet_vnd_newlink(u8 id, struct net_device *rmnet_dev,
struct rmnet_port *port,
struct net_device *real_dev,
struct rmnet_endpoint *ep,
- struct netlink_ext_ack *extack)
-
+ struct netlink_ext_ack *extack, u32 data_format)
{
struct rmnet_priv *priv = netdev_priv(rmnet_dev);
u32 headroom;
@@ -326,9 +334,11 @@ int rmnet_vnd_newlink(u8 id, struct net_device *rmnet_dev,
priv->real_dev = real_dev;
- headroom = rmnet_vnd_headroom(port);
+ headroom = rmnet_vnd_headroom(data_format);
- if (rmnet_vnd_change_mtu(rmnet_dev, real_dev->mtu - headroom)) {
+ if (rmnet_vnd_change_mtu_with_format(rmnet_dev,
+ real_dev->mtu - headroom,
+ data_format)) {
NL_SET_ERR_MSG_MOD(extack, "Invalid MTU on real dev");
return -EINVAL;
}
@@ -375,17 +385,15 @@ int rmnet_vnd_do_flow_control(struct net_device *rmnet_dev, int enable)
return 0;
}
-int rmnet_vnd_validate_real_dev_mtu(struct net_device *real_dev)
+static int rmnet_vnd_validate_mtu(struct rmnet_port *port,
+ struct net_device *real_dev, u32 data_format)
{
struct hlist_node *tmp_ep;
struct rmnet_endpoint *ep;
- struct rmnet_port *port;
unsigned long bkt_ep;
u32 headroom;
- port = rmnet_get_port_rtnl(real_dev);
-
- headroom = rmnet_vnd_headroom(port);
+ headroom = rmnet_vnd_headroom(data_format);
hash_for_each_safe(port->muxed_ep, bkt_ep, tmp_ep, ep, hlnode) {
if (ep->egress_dev->mtu > (real_dev->mtu - headroom))
@@ -395,23 +403,39 @@ int rmnet_vnd_validate_real_dev_mtu(struct net_device *real_dev)
return 0;
}
+int rmnet_vnd_validate_real_dev_mtu(struct net_device *real_dev)
+{
+ struct rmnet_port *port;
+
+ port = rmnet_get_port_rtnl(real_dev);
+
+ return rmnet_vnd_validate_mtu(port, real_dev,
+ READ_ONCE(port->data_format));
+}
+
int rmnet_vnd_update_dev_mtu(struct rmnet_port *port,
- struct net_device *real_dev)
+ struct net_device *real_dev, u32 data_format)
{
struct hlist_node *tmp_ep;
struct rmnet_endpoint *ep;
unsigned long bkt_ep;
u32 headroom;
+ int new_mtu;
- headroom = rmnet_vnd_headroom(port);
+ headroom = rmnet_vnd_headroom(data_format);
+ if (real_dev->mtu < headroom)
+ return -EINVAL;
+
+ new_mtu = real_dev->mtu - headroom;
+ if (new_mtu > RMNET_MAX_PACKET_SIZE)
+ return -EINVAL;
hash_for_each_safe(port->muxed_ep, bkt_ep, tmp_ep, ep, hlnode) {
- if (ep->egress_dev->mtu <= (real_dev->mtu - headroom))
+ if (ep->egress_dev->mtu <= new_mtu)
continue;
- if (rmnet_vnd_change_mtu(ep->egress_dev,
- real_dev->mtu - headroom))
- return -1;
+ /* The target MTU was validated before updating any endpoint. */
+ WRITE_ONCE(ep->egress_dev->mtu, new_mtu);
}
return 0;
diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_vnd.h b/drivers/net/ethernet/qualcomm/rmnet/rmnet_vnd.h
index c2b2baf86894..901ef36900ac 100644
--- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_vnd.h
+++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_vnd.h
@@ -12,7 +12,7 @@ int rmnet_vnd_newlink(u8 id, struct net_device *rmnet_dev,
struct rmnet_port *port,
struct net_device *real_dev,
struct rmnet_endpoint *ep,
- struct netlink_ext_ack *extack);
+ struct netlink_ext_ack *extack, u32 data_format);
int rmnet_vnd_dellink(u8 id, struct rmnet_port *port,
struct rmnet_endpoint *ep);
void rmnet_vnd_rx_fixup(struct sk_buff *skb, struct net_device *dev);
@@ -21,5 +21,5 @@ void rmnet_vnd_tx_fixup(struct sk_buff *skb, struct net_device *dev);
void rmnet_vnd_setup(struct net_device *dev);
int rmnet_vnd_validate_real_dev_mtu(struct net_device *real_dev);
int rmnet_vnd_update_dev_mtu(struct rmnet_port *port,
- struct net_device *real_dev);
+ struct net_device *real_dev, u32 data_format);
#endif /* _RMNET_VND_H_ */
--
2.34.1
next prev parent reply other threads:[~2026-10-08 0:57 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-08 0:55 [PATCH net-next v2 0/8] Add HW GRO handling in rmnet Subash Abhinov Kasiviswanathan
2026-10-08 0:55 ` Subash Abhinov Kasiviswanathan [this message]
2026-10-08 0:55 ` [PATCH net-next v2 2/8] uapi: if_link: Add RMNET_FLAGS_INGRESS_COALESCE Subash Abhinov Kasiviswanathan
2026-10-08 0:55 ` [PATCH net-next v2 3/8] net: qualcomm: rmnet: Process MAPv5 frames as a list Subash Abhinov Kasiviswanathan
2026-10-08 0:55 ` [PATCH net-next v2 4/8] net: qualcomm: rmnet: Restrict supported MAP checksum configurations Subash Abhinov Kasiviswanathan
2026-10-08 0:55 ` [PATCH net-next v2 5/8] net: qualcomm: rmnet: Add DL packet coalescing support Subash Abhinov Kasiviswanathan
2026-10-08 0:55 ` [PATCH net-next v2 6/8] net: qualcomm: rmnet: Work around coalescing hardware quirks Subash Abhinov Kasiviswanathan
2026-10-08 0:55 ` [PATCH net-next v2 7/8] net: qualcomm: rmnet: Add DL coalescing statistics Subash Abhinov Kasiviswanathan
2026-10-08 23:59 ` kernel test robot
2026-10-08 0:55 ` [PATCH net-next v2 8/8] docs: networking: Add documentation for the coalescing support in rmnet Subash Abhinov Kasiviswanathan
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20261008005543.2630828-2-subash.a.kasiviswanathan@oss.qualcomm.com \
--to=subash.a.kasiviswanathan@oss.qualcomm.com \
--cc=andrew+netdev@lunn.ch \
--cc=corbet@lwn.net \
--cc=davem@davemloft.net \
--cc=edumazet@google.com \
--cc=horms@kernel.org \
--cc=kuba@kernel.org \
--cc=linux-doc@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=netdev@vger.kernel.org \
--cc=pabeni@redhat.com \
--cc=rdunlap@infradead.org \
--cc=sean.tranchetti@oss.qualcomm.com \
--cc=skhan@linuxfoundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox