From e3377f36ca20a034dce56335dc9b89f41094d845 Mon Sep 17 00:00:00 2001 From: Zoltan Kiss Date: Thu, 6 Mar 2014 21:48:29 +0000 Subject: xen-netback: Handle guests with too many frags Xen network protocol had implicit dependency on MAX_SKB_FRAGS. Netback has to handle guests sending up to XEN_NETBK_LEGACY_SLOTS_MAX slots. To achieve that: - create a new skb - map the leftover slots to its frags (no linear buffer here!) - chain it to the previous through skb_shinfo(skb)->frag_list - map them - copy and coalesce the frags into a brand new one and send it to the stack - unmap the 2 old skb's pages It's also introduces new stat counters, which help determine how often the guest sends a packet with more than MAX_SKB_FRAGS frags. NOTE: if bisect brought you here, you should apply the series up until "xen-netback: Timeout packets in RX path", otherwise malicious guests can block other guests by not releasing their sent packets. Signed-off-by: Zoltan Kiss Signed-off-by: David S. Miller --- drivers/net/xen-netback/interface.c | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'drivers/net/xen-netback/interface.c') diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c index 44df8581b4d7..b646039e539b 100644 --- a/drivers/net/xen-netback/interface.c +++ b/drivers/net/xen-netback/interface.c @@ -253,6 +253,13 @@ static const struct xenvif_stat { "tx_zerocopy_fail", offsetof(struct xenvif, tx_zerocopy_fail) }, + /* Number of packets exceeding MAX_SKB_FRAG slots. You should use + * a guest with the same MAX_SKB_FRAG + */ + { + "tx_frag_overflow", + offsetof(struct xenvif, tx_frag_overflow) + }, }; static int xenvif_get_sset_count(struct net_device *dev, int string_set) -- cgit v1.2.3