From 58d702589fd93689c142e8cb48d51877a8de3a93 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= Date: Sat, 13 Jul 2019 12:38:02 +0200 Subject: [PATCH 3/4] net: Transmit zero UDP checksum as 0xFFFF MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit RH-Author: Philippe Mathieu-Daudé 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 RH-Acked-by: Stefan Hajnoczi RH-Acked-by: Stefano Garzarella From: 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 Signed-off-by: Jason Wang (cherry picked from commit 0dacea92d26c31d453c58de2e99c178fee554166) [PMD: conflicts: hw/net/net_rx_pkt.c hw/net/vmxnet3.c] Signed-off-by: Philippe Mathieu-Daudé Signed-off-by: Miroslav Rezanina --- 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