This patch introduces the possibility to modify the MTU of the Ethernet
interface with a maximum value of 2024 (as reported in RouterOS). The real MTU
value applicable to the interface is computed as difference between the maximum
frame length (2024) minus some overhead.
The default MTU size is unchanged; if large frames are desired, ifconfig
must be used to set the new MTU.
Signed-off-by: Robert Bradley <robert.bradley1 at gmail.com>
Signed-off-by: Antonio Quartulli <or...@autistici.org>
---
.../drivers/net/ethernet/atheros/ag71xx/ag71xx.h | 19 +++++++++++++++++--
.../drivers/net/ethernet/atheros/ag71xx/ag71xx_main.c | 18 +++++++++++++++++-
2 files changed, 34 insertions(+), 3 deletions(-)
diff --git
a/target/linux/ar71xx/files/drivers/net/ethernet/atheros/ag71xx/ag71xx.h
b/target/linux/ar71xx/files/drivers/net/ethernet/atheros/ag71xx/ag71xx.h
index b9d95ad..c63c3d7 100644
--- a/target/linux/ar71xx/files/drivers/net/ethernet/atheros/ag71xx/ag71xx.h
+++ b/target/linux/ar71xx/files/drivers/net/ethernet/atheros/ag71xx/ag71xx.h
@@ -50,9 +50,24 @@
#define AG71XX_INT_POLL (AG71XX_INT_RX | AG71XX_INT_TX)
#define AG71XX_INT_INIT (AG71XX_INT_ERR | AG71XX_INT_POLL)
-#define AG71XX_TX_MTU_LEN 1540
+#define AG71XX_TX_MTU_LEN 2024
+/*
+ * AG71XX_MAX_DATA_LEN equals the maximum possible MTU that a frame of length
+ * AG71XX_TX_MTU_LEN can have. This may be larger than ETH_DATA_LEN! This
+ * define is necessary for baby jumbo packet support (as per RFC 4638).
+ *
+ * Redefining this as ETH_DATA_LEN restores the 1500-octet MTU limit.
+ */
+#define AG71XX_MAX_DATA_LEN \
+ (AG71XX_TX_MTU_LEN - (ETH_FCS_LEN + VLAN_HLEN + ETH_HLEN))
+/*
+ * Define AG71XX_RX_PKT_SIZE using AG71XX_MAX_DATA_LEN + ETH_HLEN rather than
+ * ETH_FRAME_LEN so that baby jumbo frames can be used safely. This definition
+ * means that setting AG71XX_MAX_DATA_LEN to ETH_DATA_LEN restores the old
+ * values, which are safe for standard frames.
+ */
#define AG71XX_RX_PKT_SIZE \
- (ETH_FRAME_LEN + ETH_FCS_LEN + VLAN_HLEN)
+ (AG71XX_MAX_DATA_LEN + ETH_HLEN + ETH_FCS_LEN + VLAN_HLEN)
#define AG71XX_RX_BUF_SIZE (AG71XX_RX_PKT_SIZE + NET_SKB_PAD + NET_IP_ALIGN)
#define AG71XX_TX_RING_SIZE_DEFAULT 64
diff --git
a/target/linux/ar71xx/files/drivers/net/ethernet/atheros/ag71xx/ag71xx_main.c
b/target/linux/ar71xx/files/drivers/net/ethernet/atheros/ag71xx/ag71xx_main.c
index fb99d27..d3e850b 100644
---
a/target/linux/ar71xx/files/drivers/net/ethernet/atheros/ag71xx/ag71xx_main.c
+++
b/target/linux/ar71xx/files/drivers/net/ethernet/atheros/ag71xx/ag71xx_main.c
@@ -1042,13 +1042,29 @@ static void ag71xx_netpoll(struct net_device *dev)
}
#endif
+/*
+ * ag71xx_change_mtu: set interface MTU.
+ * A modified eth_change_mtu, changing the upper limit from ETH_DATA_LEN to
+ * AG71XX_MAX_DATA_LEN. This means that baby jumbo packets may be used by
+ * PPPoE users, assuming that AG71XX_MAX_DATA_LEN > ETH_DATA_LEN.
+ *
+ * Returns 0 on success, -EINVAL otherwise.
+ */
+static int ag71xx_change_mtu(struct net_device *dev, int new_mtu)
+{
+ if (new_mtu < 68 || new_mtu > AG71XX_MAX_DATA_LEN)
+ return -EINVAL;
+ dev->mtu = new_mtu;
+ return 0;
+}
+
static const struct net_device_ops ag71xx_netdev_ops = {
.ndo_open = ag71xx_open,
.ndo_stop = ag71xx_stop,
.ndo_start_xmit = ag71xx_hard_start_xmit,
.ndo_do_ioctl = ag71xx_do_ioctl,
.ndo_tx_timeout = ag71xx_tx_timeout,
- .ndo_change_mtu = eth_change_mtu,
+ .ndo_change_mtu = ag71xx_change_mtu,
.ndo_set_mac_address = eth_mac_addr,
.ndo_validate_addr = eth_validate_addr,
#ifdef CONFIG_NET_POLL_CONTROLLER
--
1.7.12
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