Re: [PATCH v2 1/1] net: macb: initialize checksum when using checksum offloading
From: David Miller <davem@davemloft.net>
Date: 2016-09-01 21:52:31
From: Helmut Buchsbaum <redacted> Date: Mon, 29 Aug 2016 15:57:25 +0200
quoted hunk ↗ jump to hunk
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()