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ibmveth: Set CHECKSUM_PARTIAL if NULL TCP CSUM.

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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: David Wilder <dwilder@us.ibm.com>
Reviewed-by: Pradeep Satyanarayana <pradeeps@linux.vnet.ibm.com>
Tested-by: Cristobal Forno <cforno12@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David Wilder 2021-06-22 14:52:15 -07:00 committed by David S. Miller
parent fe87797bf2
commit 7525de2516
1 changed files with 28 additions and 23 deletions
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51
drivers/net/ethernet/ibm/ibmveth.c
View file

@ -1285,36 +1285,41 @@ static void ibmveth_rx_csum_helper(struct sk_buff *skb,
iph_proto = iph6->nexthdr; iph_proto = iph6->nexthdr;
} }
/* In OVS environment, when a flow is not cached, specifically for a /* When CSO is enabled the TCP checksum may have be set to NULL by
* new TCP connection, the first packet information is passed up * 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 * the user space for finding a flow. During this process, OVS computes
* checksum on the first packet when CHECKSUM_PARTIAL flag is set. * checksum on the first packet when CHECKSUM_PARTIAL flag is set.
* *
* Given that we zeroed out TCP checksum field in transmit path * So, re-compute TCP pseudo header checksum when configured for
* (refer ibmveth_start_xmit routine) as we set "no checksum bit", * trunk mode.
* 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.
*/ */
if (iph_proto == IPPROTO_TCP && adapter->is_active_trunk) { if (iph_proto == IPPROTO_TCP) {
struct tcphdr *tcph = (struct tcphdr *)(skb->data + iphlen); struct tcphdr *tcph = (struct tcphdr *)(skb->data + iphlen);
if (tcph->check == 0x0000) {
tcphdrlen = skb->len - iphlen; /* Recompute TCP pseudo header checksum */
if (adapter->is_active_trunk) {
/* Recompute TCP pseudo header checksum */ tcphdrlen = skb->len - iphlen;
if (skb_proto == ETH_P_IP) 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); iph->daddr, tcphdrlen, iph_proto, 0);
else if (skb_proto == ETH_P_IPV6) 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); &iph6->daddr, tcphdrlen, iph_proto, 0);
}
/* Setup SKB fields for checksum offload */ /* Setup SKB fields for checksum offload */
skb_partial_csum_set(skb, iphlen, skb_partial_csum_set(skb, iphlen,
offsetof(struct tcphdr, check)); offsetof(struct tcphdr, check));
skb_reset_network_header(skb); skb_reset_network_header(skb);
}
} }
} }