LWIP_NETIF_TX_SINGLE_PBUF macro

LWIP_NETIF_TX_SINGLE_PBUF: if this is set to 1, lwIP *tries* to put all data to be sent into one single pbuf. This is for compatibility with DMA-enabled MACs that do not support scatter-gather. Beware that this might involve CPU-memcpy before transmitting that would not be needed without this flag! Use this only if you need to! ATTENTION: a driver should *NOT* rely on getting single pbufs but check TX pbufs for being in one piece. If not, pbuf_clone can be used to get a single pbuf: if (p->next != NULL) { struct pbuf *q = pbuf_clone(PBUF_RAW, PBUF_RAM, p); if (q == NULL) { return ERR_MEM; } p = q; ATTENTION: do NOT free the old 'p' as the ref belongs to the caller! }