From 58d702589fd93689c142e8cb48d51877a8de3a93 Mon Sep 17 00:00:00 2001

From: =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= <philmd@redhat.com>

Date: Sat, 13 Jul 2019 12:38:02 +0200

Subject: [PATCH 3/4] net: Transmit zero UDP checksum as 0xFFFF

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RH-Author: Philippe Mathieu-Daudé <philmd@redhat.com>

Message-id: <20190713123802.23932-3-philmd@redhat.com>

Patchwork-id: 89509

O-Subject: [RHEL-7.7 qemu-kvm PATCH 2/2] net: Transmit zero UDP checksum as 0xFFFF

Bugzilla: 1270166

RH-Acked-by: Xiao Wang <jasowang@redhat.com>

RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>

RH-Acked-by: Stefano Garzarella <sgarzare@redhat.com>

From: Ed Swierk <eswierk@skyportsystems.com>

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>

Signed-off-by: Jason Wang <jasowang@redhat.com>

(cherry picked from commit 0dacea92d26c31d453c58de2e99c178fee554166)

[PMD: conflicts: hw/net/net_rx_pkt.c hw/net/vmxnet3.c]

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>

---

 hw/net/e1000.c         | 2 +-

 hw/net/vmxnet_tx_pkt.c | 2 +-

 include/net/checksum.h | 6 ++++++

 3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/hw/net/e1000.c b/hw/net/e1000.c

index 711d369..d876949 100644

--- a/hw/net/e1000.c

+++ b/hw/net/e1000.c

@@ -442,7 +442,7 @@ 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/vmxnet_tx_pkt.c b/hw/net/vmxnet_tx_pkt.c

index fc01e4d..03f34cf 100644

--- a/hw/net/vmxnet_tx_pkt.c

+++ b/hw/net/vmxnet_tx_pkt.c

@@ -437,7 +437,7 @@ static void vmxnet_tx_pkt_do_sw_csum(struct VmxnetTxPkt *pkt)

     csum_cntr += eth_calc_pseudo_hdr_csum(iphdr, csl);

     /* 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/include/net/checksum.h b/include/net/checksum.h

index 80203fb..78b7d9b 100644

--- a/include/net/checksum.h

+++ b/include/net/checksum.h

@@ -33,6 +33,12 @@ 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));

-- 

1.8.3.1