S_TX_SNDBUF
#define V_TX_SNDBUF(x) ((x) << S_TX_SNDBUF)
#define G_TX_SNDBUF(x) (((x) >> S_TX_SNDBUF) & M_TX_SNDBUF)
#define V_TX_SNDBUF(x) ((x) << S_TX_SNDBUF)
#define G_TX_SNDBUF(x) (((x) >> S_TX_SNDBUF) & M_TX_SNDBUF)