VGE_MAXTXSEGS
bus_dma_segment_t txsegs[VGE_MAXTXSEGS];
m = m_collapse(*m_head, M_NOWAIT, VGE_MAXTXSEGS);
MCLBYTES * VGE_MAXTXSEGS, /* maxsize */
VGE_MAXTXSEGS, /* nsegments */