How big buffer should I supply to the DHCP_init() function?

Question

How big buffer should I supply to the DHCP_init() function? I can see in the driver the following: void DHCP_init(uint8_t s, uint8_t * buf) { uint8_t zeroip[4] = {0,0,0,0}; getSHAR(DHCP_CHADDR); if((DHCP_CHADDR[0] | DHCP_CHADDR[1] | DHCP_CHADDR[2] | DHCP_CHADDR[3] | DHCP_CHADDR[4] | DHCP_CHADDR[5]) == 0x00) { // assing temporary mac address, you should be set SHAR before call this function. DHCP_CHADDR[0] = 0x00; DHCP_CHADDR[1] = 0x08; DHCP_CHADDR[2] = 0xdc; DHCP_CHADDR[3] = 0x00; DHCP_CHADDR[4] = 0x00; DHCP_CHADDR[5] = 0x00; setSHAR(DHCP_CHADDR); } DHCP_SOCKET = s; // SOCK_DHCP pDHCPMSG = (RIP_MSG*)buf; DHCP_XID = 0x12345678; // WIZchip Netinfo Clear setSIPR(zeroip); setSIPR(zeroip); setGAR(zeroip); reset_DHCP_timeout(); dhcp_state = STATE_DHCP_INIT; } and /* * @brief DHCP message format */ typedef struct { uint8_t op; ///< @ref DHCP_BOOTREQUEST or @ref DHCP_BOOTREPLY uint8_t htype; ///< @ref DHCP_HTYPE10MB or @ref DHCP_HTYPE100MB uint8_t hlen; ///< @ref DHCP_HLENETHERNET uint8_t hops; ///< @ref DHCP_HOPS uint32_t xid; ///< @ref DHCP_XID This increase one every DHCP transaction. uint16_t secs; ///< @ref DHCP_SECS uint16_t flags; ///< @ref DHCP_FLAGSBROADCAST or @ref DHCP_FLAGSUNICAST uint8_t ciaddr[4]; ///< @ref Request IP to DHCP sever uint8_t yiaddr[4]; ///< @ref Offered IP from DHCP server uint8_t siaddr[4]; ///< No use uint8_t giaddr[4]; ///< No use uint8_t chaddr[16]; ///< DHCP client 6bytes MAC address. Others is filled to zero uint8_t sname[64]; ///< No use uint8_t file[128]; ///< No use uint8_t OPT[OPT_SIZE]; ///< Option } RIP_MSG; and #define OPT_SIZE 312 /// Max OPT size of @ref RIP_MSG #define RIP_MSG_SIZE (236+OPT_SIZE) /// Max size of @ref RIP_MSG So 548 byte would be ok?

Coccoliso · Answer

1K is sufficient but keep in mind that after you’ve gotten the address you can easily reuse the socket then put the buffer size that you need to use in your application.