* [Qemu-devel] [PATCH v3 REPOST] net: Transmit zero UDP checksum as 0xFFFF
@ 2017-11-16 14:06 Ed Swierk
2017-11-17 3:00 ` Jason Wang
0 siblings, 1 reply; 2+ messages in thread
From: Ed Swierk @ 2017-11-16 14:06 UTC (permalink / raw)
To: Jason Wang, Daniel P . Berrange, Stefan Hajnoczi, Dmitry Fleytman
Cc: qemu-devel, Ed Swierk
The checksum algorithm used by IPv4, TCP and UDP allows a zero value
to be represented by either 0x0000 and 0xFFFF. But per RFC 768, a zero
UDP checksum must be transmitted as 0xFFFF because 0x0000 is a special
value meaning no checksum.
Substitute 0xFFFF whenever a checksum is computed as zero when
modifying a UDP datagram header. Doing this on IPv4 and TCP checksums
is unnecessary but legal. Add a wrapper for net_checksum_finish() that
makes the substitution.
(We can't just change net_checksum_finish(), as that function is also
used by receivers to verify checksums, and in that case the expected
value is always 0x0000.)
Signed-off-by: Ed Swierk <eswierk@skyportsystems.com>
---
v3:
(Reposted to fix patch format)
Leave net_tx_pkt_update_ip_checksums() alone since it's only computing
a partial sum of the IP pseudo-header.
Rename wrapper to net_checksum_finish_nozero() for clarity.
v2:
Add a wrapper net_checksum_finish_hdr() rather than duplicating the
logic at every caller.
---
hw/net/e1000.c | 2 +-
hw/net/net_rx_pkt.c | 2 +-
hw/net/net_tx_pkt.c | 2 +-
hw/net/vmxnet3.c | 3 ++-
include/net/checksum.h | 6 ++++++
5 files changed, 11 insertions(+), 4 deletions(-)
diff --git a/hw/net/e1000.c b/hw/net/e1000.c
index 72a92be..804ec08 100644
--- a/hw/net/e1000.c
+++ b/hw/net/e1000.c
@@ -506,7 +506,7 @@ putsum(uint8_t *data, uint32_t n, uint32_t sloc, uint32_t css, uint32_t cse)
n = cse + 1;
if (sloc < n-1) {
sum = net_checksum_add(n-css, data+css);
- stw_be_p(data + sloc, net_checksum_finish(sum));
+ stw_be_p(data + sloc, net_checksum_finish_nozero(sum));
}
}
diff --git a/hw/net/net_rx_pkt.c b/hw/net/net_rx_pkt.c
index cef1c2e..98a5030 100644
--- a/hw/net/net_rx_pkt.c
+++ b/hw/net/net_rx_pkt.c
@@ -518,7 +518,7 @@ _net_rx_pkt_calc_l4_csum(struct NetRxPkt *pkt)
cntr += net_checksum_add_iov(pkt->vec, pkt->vec_len,
pkt->l4hdr_off, csl, cso);
- csum = net_checksum_finish(cntr);
+ csum = net_checksum_finish_nozero(cntr);
trace_net_rx_pkt_l4_csum_calc_csum(pkt->l4hdr_off, csl, cntr, csum);
diff --git a/hw/net/net_tx_pkt.c b/hw/net/net_tx_pkt.c
index 20b2549..e29c881 100644
--- a/hw/net/net_tx_pkt.c
+++ b/hw/net/net_tx_pkt.c
@@ -486,7 +486,7 @@ static void net_tx_pkt_do_sw_csum(struct NetTxPkt *pkt)
net_checksum_add_iov(iov, iov_len, pkt->virt_hdr.csum_start, csl, cso);
/* Put the checksum obtained into the packet */
- csum = cpu_to_be16(net_checksum_finish(csum_cntr));
+ csum = cpu_to_be16(net_checksum_finish_nozero(csum_cntr));
iov_from_buf(iov, iov_len, csum_offset, &csum, sizeof csum);
}
diff --git a/hw/net/vmxnet3.c b/hw/net/vmxnet3.c
index 8c4bae5..cdc307d 100644
--- a/hw/net/vmxnet3.c
+++ b/hw/net/vmxnet3.c
@@ -972,7 +972,8 @@ static void vmxnet3_rx_need_csum_calculate(struct NetRxPkt *pkt,
data = (uint8_t *)pkt_data + vhdr->csum_start;
len = pkt_len - vhdr->csum_start;
/* Put the checksum obtained into the packet */
- stw_be_p(data + vhdr->csum_offset, net_raw_checksum(data, len));
+ stw_be_p(data + vhdr->csum_offset,
+ net_checksum_finish_nozero(net_checksum_add(len, data)));
vhdr->flags &= ~VIRTIO_NET_HDR_F_NEEDS_CSUM;
vhdr->flags |= VIRTIO_NET_HDR_F_DATA_VALID;
diff --git a/include/net/checksum.h b/include/net/checksum.h
index 7df472c..05a0d27 100644
--- a/include/net/checksum.h
+++ b/include/net/checksum.h
@@ -34,6 +34,12 @@ net_checksum_add(int len, uint8_t *buf)
}
static inline uint16_t
+net_checksum_finish_nozero(uint32_t sum)
+{
+ return net_checksum_finish(sum) ?: 0xFFFF;
+}
+
+static inline uint16_t
net_raw_checksum(uint8_t *data, int length)
{
return net_checksum_finish(net_checksum_add(length, data));
--
1.9.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [Qemu-devel] [PATCH v3 REPOST] net: Transmit zero UDP checksum as 0xFFFF
2017-11-16 14:06 [Qemu-devel] [PATCH v3 REPOST] net: Transmit zero UDP checksum as 0xFFFF Ed Swierk
@ 2017-11-17 3:00 ` Jason Wang
0 siblings, 0 replies; 2+ messages in thread
From: Jason Wang @ 2017-11-17 3:00 UTC (permalink / raw)
To: Ed Swierk, Daniel P . Berrange, Stefan Hajnoczi, Dmitry Fleytman
Cc: qemu-devel
On 2017年11月16日 22:06, Ed Swierk wrote:
> The checksum algorithm used by IPv4, TCP and UDP allows a zero value
> to be represented by either 0x0000 and 0xFFFF. But per RFC 768, a zero
> UDP checksum must be transmitted as 0xFFFF because 0x0000 is a special
> value meaning no checksum.
>
> Substitute 0xFFFF whenever a checksum is computed as zero when
> modifying a UDP datagram header. Doing this on IPv4 and TCP checksums
> is unnecessary but legal. Add a wrapper for net_checksum_finish() that
> makes the substitution.
>
> (We can't just change net_checksum_finish(), as that function is also
> used by receivers to verify checksums, and in that case the expected
> value is always 0x0000.)
>
> Signed-off-by: Ed Swierk <eswierk@skyportsystems.com>
> ---
> v3:
>
> (Reposted to fix patch format)
>
> Leave net_tx_pkt_update_ip_checksums() alone since it's only computing
> a partial sum of the IP pseudo-header.
>
> Rename wrapper to net_checksum_finish_nozero() for clarity.
>
> v2:
>
> Add a wrapper net_checksum_finish_hdr() rather than duplicating the
> logic at every caller.
> ---
> hw/net/e1000.c | 2 +-
> hw/net/net_rx_pkt.c | 2 +-
> hw/net/net_tx_pkt.c | 2 +-
> hw/net/vmxnet3.c | 3 ++-
> include/net/checksum.h | 6 ++++++
> 5 files changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/hw/net/e1000.c b/hw/net/e1000.c
> index 72a92be..804ec08 100644
> --- a/hw/net/e1000.c
> +++ b/hw/net/e1000.c
> @@ -506,7 +506,7 @@ putsum(uint8_t *data, uint32_t n, uint32_t sloc, uint32_t css, uint32_t cse)
> n = cse + 1;
> if (sloc < n-1) {
> sum = net_checksum_add(n-css, data+css);
> - stw_be_p(data + sloc, net_checksum_finish(sum));
> + stw_be_p(data + sloc, net_checksum_finish_nozero(sum));
> }
> }
>
> diff --git a/hw/net/net_rx_pkt.c b/hw/net/net_rx_pkt.c
> index cef1c2e..98a5030 100644
> --- a/hw/net/net_rx_pkt.c
> +++ b/hw/net/net_rx_pkt.c
> @@ -518,7 +518,7 @@ _net_rx_pkt_calc_l4_csum(struct NetRxPkt *pkt)
> cntr += net_checksum_add_iov(pkt->vec, pkt->vec_len,
> pkt->l4hdr_off, csl, cso);
>
> - csum = net_checksum_finish(cntr);
> + csum = net_checksum_finish_nozero(cntr);
>
> trace_net_rx_pkt_l4_csum_calc_csum(pkt->l4hdr_off, csl, cntr, csum);
>
> diff --git a/hw/net/net_tx_pkt.c b/hw/net/net_tx_pkt.c
> index 20b2549..e29c881 100644
> --- a/hw/net/net_tx_pkt.c
> +++ b/hw/net/net_tx_pkt.c
> @@ -486,7 +486,7 @@ static void net_tx_pkt_do_sw_csum(struct NetTxPkt *pkt)
> net_checksum_add_iov(iov, iov_len, pkt->virt_hdr.csum_start, csl, cso);
>
> /* Put the checksum obtained into the packet */
> - csum = cpu_to_be16(net_checksum_finish(csum_cntr));
> + csum = cpu_to_be16(net_checksum_finish_nozero(csum_cntr));
> iov_from_buf(iov, iov_len, csum_offset, &csum, sizeof csum);
> }
>
> diff --git a/hw/net/vmxnet3.c b/hw/net/vmxnet3.c
> index 8c4bae5..cdc307d 100644
> --- a/hw/net/vmxnet3.c
> +++ b/hw/net/vmxnet3.c
> @@ -972,7 +972,8 @@ static void vmxnet3_rx_need_csum_calculate(struct NetRxPkt *pkt,
> data = (uint8_t *)pkt_data + vhdr->csum_start;
> len = pkt_len - vhdr->csum_start;
> /* Put the checksum obtained into the packet */
> - stw_be_p(data + vhdr->csum_offset, net_raw_checksum(data, len));
> + stw_be_p(data + vhdr->csum_offset,
> + net_checksum_finish_nozero(net_checksum_add(len, data)));
>
> vhdr->flags &= ~VIRTIO_NET_HDR_F_NEEDS_CSUM;
> vhdr->flags |= VIRTIO_NET_HDR_F_DATA_VALID;
> diff --git a/include/net/checksum.h b/include/net/checksum.h
> index 7df472c..05a0d27 100644
> --- a/include/net/checksum.h
> +++ b/include/net/checksum.h
> @@ -34,6 +34,12 @@ net_checksum_add(int len, uint8_t *buf)
> }
>
> static inline uint16_t
> +net_checksum_finish_nozero(uint32_t sum)
> +{
> + return net_checksum_finish(sum) ?: 0xFFFF;
> +}
> +
> +static inline uint16_t
> net_raw_checksum(uint8_t *data, int length)
> {
> return net_checksum_finish(net_checksum_add(length, data));
Applied, thanks.
^ permalink raw reply [flat|nested] 2+ messages in thread
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2017-11-17 3:00 ` Jason Wang
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