When sending intra-pan packets (i.e. packets where the source and destination PANs are identical), the source PAN should be omitted from the header and the "intra-pan" bit set to 1. From the 802.15.4-2003 spec (page 154):

If the PAN identifiers are identical, the intra-PAN subfield of the frame control field shall be set to 1, and the source PAN identifier shall be omitted from the transmitted frame.

Currently, drivers using RIOT's ieee802154 implementation are sending out intra-pan packets with both source and destination PANs in the header, and the "intra-pan" bit set to 0, even though the PANs are identical. Linux will actually drop these incorrectly constructed packets.