_S_un
} _S_un;
#define s_addr _S_un._S_addr /* should be used for all code */
#define s_host _S_un._S_un_b.s_b2 /* OBSOLETE: host on imp */
#define s_net _S_un._S_un_b.s_b1 /* OBSOLETE: network */
#define s_imp _S_un._S_un_w.s_w2 /* OBSOLETE: imp */
#define s_impno _S_un._S_un_b.s_b4 /* OBSOLETE: imp # */
#define s_lh _S_un._S_un_b.s_b3 /* OBSOLETE: logical host */
((v4)->_S_un._S_un_b.s_b1 = (v6)->_S6_un._S6_u8[2], \
(v4)->_S_un._S_un_b.s_b2 = (v6)->_S6_un._S6_u8[3], \
(v4)->_S_un._S_un_b.s_b3 = (v6)->_S6_un._S6_u8[4], \
(v4)->_S_un._S_un_b.s_b4 = (v6)->_S6_un._S6_u8[5])
(v6)->_S6_un._S6_u8[2] = (v4)->_S_un._S_un_b.s_b1, \
(v6)->_S6_un._S6_u8[3] = (v4)->_S_un._S_un_b.s_b2, \
(v6)->_S6_un._S6_u8[4] = (v4)->_S_un._S_un_b.s_b3, \
(v6)->_S6_un._S6_u8[5] = (v4)->_S_un._S_un_b.s_b4, \
(v6)->_S6_un._S6_u8[2] = (v4)->_S_un._S_un_b.s_b1, \
(v6)->_S6_un._S6_u8[3] = (v4)->_S_un._S_un_b.s_b2, \
(v6)->_S6_un._S6_u8[4] = (v4)->_S_un._S_un_b.s_b3, \
(v6)->_S6_un._S6_u8[5] = (v4)->_S_un._S_un_b.s_b4, \