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| author | Lance Richardson <lrichard@redhat.com> | 2016-11-09 15:04:39 -0500 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2016-11-10 12:01:54 -0500 |
| commit | 0ace81ec7192201af48528c309ee0b4103021f55 (patch) | |
| tree | 31392af30d170c97f2162b616407c3b341910157 /net/ipv4/ip_output.c | |
| parent | 9b6c14d51bd2304b92f842e96172a9cc822fc77c (diff) | |
| download | lwn-0ace81ec7192201af48528c309ee0b4103021f55.tar.gz lwn-0ace81ec7192201af48528c309ee0b4103021f55.zip | |
ipv4: update comment to document GSO fragmentation cases.
This is a follow-up to commit 9ee6c5dc816a ("ipv4: allow local
fragmentation in ip_finish_output_gso()"), updating the comment
documenting cases in which fragmentation is needed for egress
GSO packets.
Suggested-by: Shmulik Ladkani <shmulik.ladkani@gmail.com>
Reviewed-by: Shmulik Ladkani <shmulik.ladkani@gmail.com>
Signed-off-by: Lance Richardson <lrichard@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/ip_output.c')
| -rw-r--r-- | net/ipv4/ip_output.c | 16 |
1 files changed, 11 insertions, 5 deletions
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c index 9403fa3850be..105908d841a3 100644 --- a/net/ipv4/ip_output.c +++ b/net/ipv4/ip_output.c @@ -244,12 +244,18 @@ static int ip_finish_output_gso(struct net *net, struct sock *sk, if (skb_gso_validate_mtu(skb, mtu)) return ip_finish_output2(net, sk, skb); - /* Slowpath - GSO segment length is exceeding the dst MTU. + /* Slowpath - GSO segment length exceeds the egress MTU. * - * This can happen in two cases: - * 1) TCP GRO packet, DF bit not set - * 2) skb arrived via virtio-net, we thus get TSO/GSO skbs directly - * from host network stack. + * This can happen in several cases: + * - Forwarding of a TCP GRO skb, when DF flag is not set. + * - Forwarding of an skb that arrived on a virtualization interface + * (virtio-net/vhost/tap) with TSO/GSO size set by other network + * stack. + * - Local GSO skb transmitted on an NETIF_F_TSO tunnel stacked over an + * interface with a smaller MTU. + * - Arriving GRO skb (or GSO skb in a virtualized environment) that is + * bridged to a NETIF_F_TSO tunnel stacked over an interface with an + * insufficent MTU. */ features = netif_skb_features(skb); BUILD_BUG_ON(sizeof(*IPCB(skb)) > SKB_SGO_CB_OFFSET); |