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| -rw-r--r-- | listen/listen.c | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/listen/listen.c b/listen/listen.c index bf60281..ca933c6 100644 --- a/listen/listen.c +++ b/listen/listen.c @@ -188,6 +188,34 @@ int main(int argc, char **argv) if (sock == -1 || sigint) break; if (ifr.ifr_hwaddr.sa_family == AF_AX25) { + if (size > 2 && *buffer == 0xcc) { + /* IP packets from the ax25 de-segmenter + are seen on socket "PF_PACKET, + SOCK_PACKET, ETH_P_ALL" without + AX.25 header (just the IP-frame), + prefixed by 0xcc (AX25_P_IP). + It's unclear why in the kernel code + this happens (unsegmentet AX25 PID + AX25_P_IP have not this behavior). + We have already displayed all the + segments and like to ignore this + data. + AX.25 packets start with a kiss + byte (buffer[0]); ax25_dump() + looks for it. + There's no kiss command 0xcc + defined; kiss bytes are checked + against & 0xf (= 0x0c), which is + also not defined. + Kiss commands may have one argument. + => 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. + */ + continue; + } display_port(sa.sa_data); #ifdef NEW_AX25_STACK ax25_dump(buffer, size, dumpstyle); |