Commit 7525de25 authored by David Wilder's avatar David Wilder Committed by David S. Miller
Browse files

ibmveth: Set CHECKSUM_PARTIAL if NULL TCP CSUM. 



TCP checksums on received packets may be set to NULL by the sender if CSO
is enabled. The hypervisor flags these packets as check-sum-ok and the
skb is then flagged CHECKSUM_UNNECESSARY. If these packets are then
forwarded the sender will not request CSO due to the CHECKSUM_UNNECESSARY
flag. The result is a TCP packet sent with a bad checksum. This change
sets up CHECKSUM_PARTIAL on these packets causing the sender to correctly
request CSUM offload.

Signed-off-by: default avatarDavid Wilder <dwilder@us.ibm.com>
Reviewed-by: default avatarPradeep Satyanarayana <pradeeps@linux.vnet.ibm.com>
Tested-by: default avatarCristobal Forno <cforno12@linux.ibm.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent fe87797b

drivers/net/ethernet/ibm/ibmveth.c

+28 −23
Original line number Diff line number Diff line
@@ -1285,38 +1285,43 @@ static void ibmveth_rx_csum_helper(struct sk_buff *skb, 
		iph_proto = iph6->nexthdr;

	}



	/* In OVS environment, when a flow is not cached, specifically for a

	 * new TCP connection, the first packet information is passed up

	/* When CSO is enabled the TCP checksum may have be set to NULL by

	 * the sender given that we zeroed out TCP checksum field in

	 * transmit path (refer ibmveth_start_xmit routine). In this case set

	 * up CHECKSUM_PARTIAL. If the packet is forwarded, the checksum will

	 * then be recalculated by the destination NIC (CSO must be enabled

	 * on the destination NIC).

	 *

	 * In an OVS environment, when a flow is not cached, specifically for a

	 * new TCP connection, the first packet information is passed up to

	 * the user space for finding a flow. During this process, OVS computes

	 * checksum on the first packet when CHECKSUM_PARTIAL flag is set.

	 *

	 * Given that we zeroed out TCP checksum field in transmit path

	 * (refer ibmveth_start_xmit routine) as we set "no checksum bit",

	 * OVS computed checksum will be incorrect w/o TCP pseudo checksum

	 * in the packet. This leads to OVS dropping the packet and hence

	 * TCP retransmissions are seen.

	 *

	 * So, re-compute TCP pseudo header checksum.

	 * So, re-compute TCP pseudo header checksum when configured for

	 * trunk mode.

	 */

	if (iph_proto == IPPROTO_TCP && adapter->is_active_trunk) {

	if (iph_proto == IPPROTO_TCP) {

		struct tcphdr *tcph = (struct tcphdr *)(skb->data + iphlen);



		tcphdrlen = skb->len - iphlen;



		if (tcph->check == 0x0000) {

			/* Recompute TCP pseudo header checksum  */

			if (adapter->is_active_trunk) {

				tcphdrlen = skb->len - iphlen;

				if (skb_proto == ETH_P_IP)

			tcph->check = ~csum_tcpudp_magic(iph->saddr,

					tcph->check =

					 ~csum_tcpudp_magic(iph->saddr,

					iph->daddr, tcphdrlen, iph_proto, 0);

				else if (skb_proto == ETH_P_IPV6)

			tcph->check = ~csum_ipv6_magic(&iph6->saddr,

					tcph->check =

					 ~csum_ipv6_magic(&iph6->saddr,

					&iph6->daddr, tcphdrlen, iph_proto, 0);



			}

			/* Setup SKB fields for checksum offload */

			skb_partial_csum_set(skb, iphlen,

					     offsetof(struct tcphdr, check));

			skb_reset_network_header(skb);

		}

	}

}



static int ibmveth_poll(struct napi_struct *napi, int budget)

{