| Message ID | 1472479045-8814-2-git-send-email-helmut.buchsbaum@gmail.com |
|---|---|
| State | Changes Requested, archived |
| Delegated to: | David Miller |
| Headers | show |
From: Helmut Buchsbaum <helmut.buchsbaum@gmail.com> Date: Mon, 29 Aug 2016 15:57:25 +0200 > diff --git a/drivers/net/ethernet/cadence/macb.c b/drivers/net/ethernet/cadence/macb.c > index 89c0cfa..de2f791 100644 > --- a/drivers/net/ethernet/cadence/macb.c > +++ b/drivers/net/ethernet/cadence/macb.c > @@ -1323,6 +1323,19 @@ dma_error: > return 0; > } > > +static inline void macb_clear_csum(struct sk_buff *skb) > +{ > + /* no change for packets without checksum offloading */ > + if (skb->ip_summed != CHECKSUM_PARTIAL) > + return; > + > + /* initialize checksum field > + * This is required - at least for Zynq, which otherwise calculates > + * wrong UDP header checksums for UDP packets with UDP data len <=2 > + */ > + *(__sum16 *)(skb->head + skb->csum_start + skb->csum_offset) = 0; > +} > + It is not valid to blindly modify the SKB contents, you must make sure that no other references to this SKB's data exist. You do this via skb_cow_head(skb, 0), which may fail. See for example drivers/net/ethernet/broadcom/tg3.c's tg3_start_xmit()
diff --git a/drivers/net/ethernet/cadence/macb.c b/drivers/net/ethernet/cadence/macb.c index 89c0cfa..de2f791 100644 --- a/drivers/net/ethernet/cadence/macb.c +++ b/drivers/net/ethernet/cadence/macb.c @@ -1323,6 +1323,19 @@ dma_error: return 0; } +static inline void macb_clear_csum(struct sk_buff *skb) +{ + /* no change for packets without checksum offloading */ + if (skb->ip_summed != CHECKSUM_PARTIAL) + return; + + /* initialize checksum field + * This is required - at least for Zynq, which otherwise calculates + * wrong UDP header checksums for UDP packets with UDP data len <=2 + */ + *(__sum16 *)(skb->head + skb->csum_start + skb->csum_offset) = 0; +} + static int macb_start_xmit(struct sk_buff *skb, struct net_device *dev) { u16 queue_index = skb_get_queue_mapping(skb); @@ -1362,6 +1375,8 @@ static int macb_start_xmit(struct sk_buff *skb, struct net_device *dev) return NETDEV_TX_BUSY; } + macb_clear_csum(skb); + /* Map socket buffer for DMA transfer */ if (!macb_tx_map(bp, queue, skb)) { dev_kfree_skb_any(skb);
MACB/GEM needs the checksum field initialized to 0 to get correct results on transmit in all cases, e.g. on Zynq, UDP packets with payload <= 2 otherwise contain a wrong checksums. Signed-off-by: Helmut Buchsbaum <helmut.buchsbaum@gmail.com> --- drivers/net/ethernet/cadence/macb.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+)