sl_compress_tcp
u_int sl_compress_tcp(struct mbuf *, struct ip *, struct slcompress *, int);
type = sl_compress_tcp(m, ip,
extern u_char sl_compress_tcp(struct mbuf *, struct ip *, struct slcompress *,
type = sl_compress_tcp(bp, pip, &bundle->ncp.ipcp.vj.cslc,