From d5df2ae0428a147b80bbb65d623f88f75d28b226 Mon Sep 17 00:00:00 2001 From: Hongzhi Guo Date: Fri, 10 Jul 2020 14:55:51 +0800 Subject: [PATCH] net: fix unneeded replacement of TCP checksum 0 MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Per RFC768: If the computed checksum is zero, it is transmitted as all ones. An all zero transmitted checksum value means that the transmitter generated no checksum. RFC793 for TCP has no such special treatment for the checksum of zero. Fixes: 6006818cfb26 ("net: new checksum functions") Cc: stable@dpdk.org Signed-off-by: Hongzhi Guo Acked-by: Olivier Matz Acked-by: Morten Brørup --- lib/librte_net/rte_ip.h | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/lib/librte_net/rte_ip.h b/lib/librte_net/rte_ip.h index 292f63fd74..a9ffc33571 100644 --- a/lib/librte_net/rte_ip.h +++ b/lib/librte_net/rte_ip.h @@ -324,8 +324,7 @@ rte_ipv4_phdr_cksum(const struct rte_ipv4_hdr *ipv4_hdr, uint64_t ol_flags) * @param l4_hdr * The pointer to the beginning of the L4 header. * @return - * The complemented checksum to set in the IP packet - * or 0 on error + * The complemented checksum to set in the IP packet. */ static inline uint16_t rte_ipv4_udptcp_cksum(const struct rte_ipv4_hdr *ipv4_hdr, const void *l4_hdr) @@ -344,7 +343,12 @@ rte_ipv4_udptcp_cksum(const struct rte_ipv4_hdr *ipv4_hdr, const void *l4_hdr) cksum = ((cksum & 0xffff0000) >> 16) + (cksum & 0xffff); cksum = (~cksum) & 0xffff; - if (cksum == 0) + /* + * Per RFC 768:If the computed checksum is zero for UDP, + * it is transmitted as all ones + * (the equivalent in one's complement arithmetic). + */ + if (cksum == 0 && ipv4_hdr->next_proto_id == IPPROTO_UDP) cksum = 0xffff; return (uint16_t)cksum; @@ -438,7 +442,12 @@ rte_ipv6_udptcp_cksum(const struct rte_ipv6_hdr *ipv6_hdr, const void *l4_hdr) cksum = ((cksum & 0xffff0000) >> 16) + (cksum & 0xffff); cksum = (~cksum) & 0xffff; - if (cksum == 0) + /* + * Per RFC 768: If the computed checksum is zero for UDP, + * it is transmitted as all ones + * (the equivalent in one's complement arithmetic). + */ + if (cksum == 0 && ipv6_hdr->proto == IPPROTO_UDP) cksum = 0xffff; return (uint16_t)cksum; -- 2.20.1