From: Robert Hancock robert.hancock@calian.com
[ Upstream commit 7b90f5a665acd46efbbfa677a3a3a18d01ad6487 ]
PTP TX timestamp handling was observed to be broken with this driver when using the raw Layer 2 PTP encapsulation. ptp4l was not receiving the expected TX timestamp after transmitting a packet, causing it to enter a failure state.
The problem appears to be due to the way that the driver pads packets which are smaller than the Ethernet minimum of 60 bytes. If headroom space was available in the SKB, this caused the driver to move the data back to utilize it. However, this appears to cause other data references in the SKB to become inconsistent. In particular, this caused the ptp_one_step_sync function to later (in the TX completion path) falsely detect the packet as a one-step SYNC packet, even when it was not, which caused the TX timestamp to not be processed when it should be.
Using the headroom for this purpose seems like an unnecessary complexity as this is not a hot path in the driver, and in most cases it appears that there is sufficient tailroom to not require using the headroom anyway. Remove this usage of headroom to prevent this inconsistency from occurring and causing other problems.
Fixes: 653e92a9175e ("net: macb: add support for padding and fcs computation") Signed-off-by: Robert Hancock robert.hancock@calian.com Reviewed-by: Jacob Keller jacob.e.keller@intel.com Tested-by: Claudiu Beznea claudiu.beznea@microchip.com # on SAMA7G5 Reviewed-by: Claudiu Beznea claudiu.beznea@microchip.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/ethernet/cadence/macb_main.c | 9 +-------- 1 file changed, 1 insertion(+), 8 deletions(-)
diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c index 4f63f1ba3161..300f47ca42e3 100644 --- a/drivers/net/ethernet/cadence/macb_main.c +++ b/drivers/net/ethernet/cadence/macb_main.c @@ -2188,7 +2188,6 @@ static int macb_pad_and_fcs(struct sk_buff **skb, struct net_device *ndev) bool cloned = skb_cloned(*skb) || skb_header_cloned(*skb) || skb_is_nonlinear(*skb); int padlen = ETH_ZLEN - (*skb)->len; - int headroom = skb_headroom(*skb); int tailroom = skb_tailroom(*skb); struct sk_buff *nskb; u32 fcs; @@ -2202,9 +2201,6 @@ static int macb_pad_and_fcs(struct sk_buff **skb, struct net_device *ndev) /* FCS could be appeded to tailroom. */ if (tailroom >= ETH_FCS_LEN) goto add_fcs; - /* FCS could be appeded by moving data to headroom. */ - else if (!cloned && headroom + tailroom >= ETH_FCS_LEN) - padlen = 0; /* No room for FCS, need to reallocate skb. */ else padlen = ETH_FCS_LEN; @@ -2213,10 +2209,7 @@ static int macb_pad_and_fcs(struct sk_buff **skb, struct net_device *ndev) padlen += ETH_FCS_LEN; }
- if (!cloned && headroom + tailroom >= padlen) { - (*skb)->data = memmove((*skb)->head, (*skb)->data, (*skb)->len); - skb_set_tail_pointer(*skb, (*skb)->len); - } else { + if (cloned || tailroom < padlen) { nskb = skb_copy_expand(*skb, 0, padlen, GFP_ATOMIC); if (!nskb) return -ENOMEM;