lisa/android_kernel_xiaomi_sm8350
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

net: macb: fix PTP TX timestamp failure due to packet padding

Browse Source 
[ 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: 653e92a917 ("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>
This commit is contained in:
Robert Hancock 2023-01-16 15:41:33 -06:00 committed by Greg Kroah-Hartman
parent 18dd3b30d4
commit d16b83c804
1 changed files with 1 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
drivers/net/ethernet/cadence/macb_main.c
View File

@ -1752,7 +1752,6 @@ 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;
@ -1766,9 +1765,6 @@ 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;
@ -1777,10 +1773,7 @@ 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;