MPLS_EXP_MASK
shim = *mtod(m, uint32_t *) & MPLS_EXP_MASK;
shim = *mtod(m, uint32_t *) & MPLS_EXP_MASK;
itos = (ntohl(shim & MPLS_EXP_MASK) >> MPLS_EXP_OFFSET) << 5;
shim = bemtoh32(mtod(m, uint32_t *)) & MPLS_EXP_MASK;
exp = ntohl(shim->shim_label & MPLS_EXP_MASK) >> MPLS_EXP_OFFSET;
exp = ntohl(shim & MPLS_EXP_MASK) >> MPLS_EXP_OFFSET;
exp = ntohl(shim->shim_label & MPLS_EXP_MASK) >> MPLS_EXP_OFFSET;
shim->shim_label &= ~MPLS_EXP_MASK;
shim->shim_label |= htonl(t) & MPLS_EXP_MASK;
#define MPLS_EXP(m) ((m & MPLS_EXP_MASK) >> MPLS_EXP_OFFSET)