Messages in this thread | | | Date | Wed, 09 Apr 2014 13:01:11 -0400 (EDT) | Subject | Re: [PATCH net 3/3] Drivers: net: hyperv: Address UDP checksum issues | From | David Miller <> |
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From: "K. Y. Srinivasan" <kys@microsoft.com> Date: Tue, 8 Apr 2014 12:46:11 -0700
> } else if (net_trans_info & INFO_UDP) { > - csum_info->transmit.udp_checksum = 1; > + /* UDP checksum offload is not supported on ws2008r2. > + * Furthermore, on ws2012 and ws2012r2, there are some > + * issues with udp checksum offload from Linux guests. > + * (these are host issues). > + * For now compute the checksum here. > + */ > + struct udphdr *uh = udp_hdr(skb); > + u16 udp_len = ntohs(uh->len); > + > + uh->check = 0; > + uh->check = csum_tcpudp_magic(ip_hdr(skb)->saddr, > + ip_hdr(skb)->daddr, > + udp_len, IPPROTO_UDP, > + csum_partial(uh, udp_len, 0)); > + if (uh->check == 0) > + uh->check = CSUM_MANGLED_0; > + > + csum_info->transmit.udp_checksum = 0;
You absolutely cannot mangle packet header contents without first COW'ing the SKB to make sure it's writable.
Otherwise network taps like tcpdump, and any other entity with a reference to the packet, can see inconsistent state.
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