From: David Miller <davem@davemloft.net>
To: kys@microsoft.com
Cc: olaf@aepfle.de, netdev@vger.kernel.org, jasowang@redhat.com,
linux-kernel@vger.kernel.org, apw@canonical.com,
devel@linuxdriverproject.org
Subject: Re: [PATCH net 3/3] Drivers: net: hyperv: Address UDP checksum issues
Date: Wed, 09 Apr 2014 13:01:11 -0400 (EDT) [thread overview]
Message-ID: <20140409.130111.1002891296248446198.davem@davemloft.net> (raw)
In-Reply-To: <1396986371-12137-4-git-send-email-kys@microsoft.com>
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.
next prev parent reply other threads:[~2014-04-09 17:01 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-08 19:45 [PATCH net 0/3] Fix issues with Heper-V network offload code K. Y. Srinivasan
2014-04-08 19:46 ` K. Y. Srinivasan
2014-04-08 19:46 ` [PATCH net 1/3] Drivers: net: hyperv: Allocate memory for all possible per-pecket information K. Y. Srinivasan
2014-04-08 19:46 ` [PATCH net 2/3] Drivers: net: hyperv: Negotiate suitable ndis version for offload support K. Y. Srinivasan
2014-04-08 19:46 ` [PATCH net 3/3] Drivers: net: hyperv: Address UDP checksum issues K. Y. Srinivasan
2014-04-09 17:01 ` David Miller [this message]
2014-04-09 18:08 ` KY Srinivasan
2014-04-09 18:36 ` David Miller
2014-04-09 18:39 ` KY Srinivasan
2014-04-09 18:42 ` David Miller
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