listen -a shows on segmented packets ok, but shows also the defragmented,

packet, but garbled:
bpq2: fm DL9SAU to DL9SAU-15 ctl I00+ pid=8(segment) len 4  remain 0
0000  E2 E3 E4                                         | ...

Reason:
the defragmented packet is passed to netif_rx(skb).
It has  skb->protocol = htons(ETH_P_IP), but still belongs to
ifr.ifr_hwaddr.sa_family == AF_AX25.
listen -a looks for every iface with like ifr.ifr_hwaddr.sa_family == AF_AX25
and thus gets the desegmented packet. This desegmented packet has already
lost his ax25 header information (it's the IP datagram that netif_rx sees),
prefixed by AX25_P_IP = 0xcc:

strace:
recvfrom(3, "\0\210\230r\246\202\252\340\210\230r\246\202\252\177\314\10\201\314E\0\1\1\0\32\0\0?\1!\327,\200\200\n,\200\200\1\0\0\347\300\21\6\0\1\26\23\303V..
                                                               recvfrom(3, "\314E\0\1\1\0\32\0\0?\1!\327,\200\200\n,\200\200\1\0\0\347\300\21\6\0\1\26\23\303V..

\314 == 0xcc == AX25_P_IP

We can make safely make the assumption for first byte == 0xcc and length > 2,
that we safeley can detect those IP frames, and then ignore it.

Signed-off-by: Thomas Osterried <ax25@x-berg.in-berlin.de>

0 files changed, 0 insertions, 0 deletions