Statistics:

kuznet@amber:~ $ ip -s tunl ls Cisco
Cisco: ipv6/ip  remote 192.31.7.104  local 192.203.80.142  ttl 32 
RX: Packets    Bytes        Errors CsumErrs OutOfSeq Mcasts
    12566      1707516      0      0        0        0       
TX: Packets    Bytes        Errors DeadLoop NoRoute  NoBufs
    13445      1879677      0      0        0        0     
kuznet@amber:~ $

Essentially, these numbers are the same as the numbers printed with ip -s link show (sec.4.2, p.) but the tags are different to reflect that they are tunnel specific.

• CsumErrs -- the total number of packets dropped because of checksum failures for a GRE tunnel with checksumming enabled.
• OutOfSeq -- the total number of packets dropped because they arrived out of sequence for a GRE tunnel with serialization enabled.
• Mcasts -- the total number of multicast packets received on a broadcast GRE tunnel.
• DeadLoop -- the total number of packets which were not transmitted because the tunnel is looped back to itself.
• NoRoute -- the total number of packets which were not transmitted because there is no IP route to the remote endpoint.
• NoBufs -- the total number of packets which were not transmitted because the kernel failed to allocate a buffer.