Le lundi 06 février 2012 à 11:31 -0500, David Miller a écrit : > We really need an explanation, probably both in the commit message and > the comments next to this new struct member, explaining why in the world > we can't use ->hard_header_len for this. OK, I added some information from Or Gerlitz in V2 Thanks ! [PATCH net-next V2] gro: introduce gro_mac_header_len Shlomo Pongratz reported GRO L2 header check was suited for Ethernet only, and failed on IB/ipoib traffic. He provided a patch faking a zeroed header to let GRO aggregates frames. Roland Dreier, Herbert Xu, and others suggested we change GRO L2 header check to be more generic. This patch introduces a new netdevice field, gro_mac_header_len, giving L2 header length, default to ETH_HLEN (14 bytes) A device setup function can override this default value. gro_max_header_len can be different than hard_header_len because as Or Gerlitz said : IPoIB advertizes hard_header_len which is bigger than the IPoIB header len, this is done such that skbs sent by the network stack have enough headroom for a "pseudoheader" which for few flows (e.g unicast arp replies and multicast) is placed there by the ipoib hard_header function and later used by the xmit function. __napi_gro_receive() has special handling for the common case (Ethernet) to avoid a memcmp() call and use an inline optimized function instead. Signed-off-by: Eric Dumazet <eric.dumazet@xxxxxxxxx> Reported-by: Shlomo Pongratz <shlomop@xxxxxxxxxxxx> Cc: Roland Dreier <roland@xxxxxxxxxx> Cc: Or Gerlitz <ogerlitz@xxxxxxxxxxxx> Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> --- V2: added a comment saying why we dont use hard_header_len but a new field. include/linux/netdevice.h | 1 + net/core/dev.c | 11 +++++++++-- 2 files changed, 10 insertions(+), 2 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 0eac07c..903bb6e 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -1095,6 +1095,7 @@ struct net_device { unsigned int mtu; /* interface MTU value */ unsigned short type; /* interface hardware type */ unsigned short hard_header_len; /* hardware hdr length */ + unsigned int gro_mac_header_len; /* L2 header length for GRO */ /* extra head- and tailroom the hardware may need, but not in all cases * can this be guaranteed, especially tailroom. Some cases also use diff --git a/net/core/dev.c b/net/core/dev.c index f124947..0b43939 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -3491,14 +3491,20 @@ static inline gro_result_t __napi_gro_receive(struct napi_struct *napi, struct sk_buff *skb) { struct sk_buff *p; + unsigned int maclen = skb->dev->gro_mac_header_len; for (p = napi->gro_list; p; p = p->next) { unsigned long diffs; diffs = (unsigned long)p->dev ^ (unsigned long)skb->dev; diffs |= p->vlan_tci ^ skb->vlan_tci; - diffs |= compare_ether_header(skb_mac_header(p), - skb_gro_mac_header(skb)); + if (maclen == ETH_HLEN) + diffs |= compare_ether_header(skb_mac_header(p), + skb_gro_mac_header(skb)); + else if (!diffs) + diffs = memcmp(skb_mac_header(p), + skb_gro_mac_header(skb), + maclen); NAPI_GRO_CB(p)->same_flow = !diffs; NAPI_GRO_CB(p)->flush = 0; } @@ -5962,6 +5968,7 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name, INIT_LIST_HEAD(&dev->unreg_list); INIT_LIST_HEAD(&dev->link_watch_list); dev->priv_flags = IFF_XMIT_DST_RELEASE; + dev->gro_mac_header_len = ETH_HLEN; setup(dev); dev->num_tx_queues = txqs; -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html