From: Ronen Arad <ronen.a...@intel.com> Date: Thu, 15 Oct 2015 01:55:17 -0700
> netlink_dump() allocates skb based on the calculated min_dump_alloc or > a per socket max_recvmsg_len. > min_alloc_size is maximum space required for any single netdev > attributes as calculated by rtnl_calcit(). > max_recvmsg_len tracks the user provided buffer to netlink_recvmsg. > It is capped at 16KiB. > The intention is to avoid small allocations and to minimize the number > of calls required to obtain dump information for all net devices. > > netlink_dump packs as many small messages as could fit within an skb > that was sized for the largest single netdev information. The actual > space available within an skb is larger than what is requested. It could > be much larger and up to near 2x with align to next power of 2 approach. > > Allowing netlink_dump to use all the space available within the > allocated skb increases the buffer size a user has to provide to avoid > truncaion (i.e. MSG_TRUNG flag set). > > It was observed that with many VLANs configured on at least one netdev, > a larger buffer of near 64KiB was necessary to avoid "Message truncated" > error in "ip link" or "bridge [-c[ompressvlans]] vlan show" when > min_alloc_size was only little over 32KiB. > > This patch trims skb to allocated size in order to allow the user to > avoid truncation with more reasonable buffer size. > > Signed-off-by: Ronen Arad <ronen.a...@intel.com> Getting spurious MSG_TRUNC is surely a bug, so I am going to apply this to 'net' as it is a genuine bug fix. Thanks. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
