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udhcp: add comments, no code changes

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Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2021-09-04 01:50:42 +02:00
parent d7e39f26d7
commit 8aa626ffff
1 changed files with 24 additions and 7 deletions
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31
networking/udhcp/common.h
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@ -38,13 +38,27 @@ struct dhcp_packet {
#define BROADCAST_FLAG 0x8000 /* "I need broadcast replies" */
uint32_t ciaddr; /* client IP (if client is in BOUND, RENEW or REBINDING state) */
uint32_t yiaddr; /* 'your' (client) IP address */
/* IP address of next server to use in bootstrap, returned in DHCPOFFER, DHCPACK by server */
/* IP address of "next server" (usually meant to be an TFTP server)
* to use in bootstrap, returned in DHCPOFFER, DHCPACK by server: */
uint32_t siaddr_nip;
uint32_t gateway_nip; /* aka 'giaddr': relay agent IP address */
/* RFC 951 (BOOTP): "place my (server) IP address in the 'siaddr' field"
* (IOW: unconditionally, not just if we are also a TFTP server).
* DHCP servers don't have to do this, they add SERVER_ID option
* to their reply packets to let client identify lease-giving server.
*/
uint32_t gateway_nip; /* aka 'giaddr': relay agent IP address, else 0 */
uint8_t chaddr[16]; /* link-layer client hardware address (MAC) */
uint8_t sname[64]; /* server host name (ASCIZ) */
/* RFC 951 (BOOTP): "If the client wishes to restrict booting
* to a particular server name, it may place [it] in 'sname'"
*/
uint8_t file[128]; /* boot file name (ASCIZ) */
uint32_t cookie; /* fixed first four option bytes (99,130,83,99 dec) */
/* RFC 951 (BOOTP): in client requests, "...can be a 'generic' name
* such as 'unix' or 'gateway'; this means 'boot the named program
* configured for my machine'"
*/
/* BOOTP fields end here, BOOTP says optional uint8_t vend[64] follows */
uint32_t cookie; /* DHCP magic bytes: 99,130,83,99 decimal */
uint8_t options[DHCP_OPTIONS_BUFSIZE + CONFIG_UDHCPC_SLACK_FOR_BUGGY_SERVERS];
};
#define DHCP_PKT_SNAME_LEN 64
@ -142,18 +156,21 @@ struct dhcp_scan_state {
//#define DHCP_NTP_SERVER 0x2a
//#define DHCP_WINS_SERVER 0x2c
#define DHCP_REQUESTED_IP 0x32 /* 50: sent by client if specific IP is wanted */
#define DHCP_LEASE_TIME 0x33 /* 51: */
#define DHCP_OPTION_OVERLOAD 0x34 /* 52: */
#define DHCP_MESSAGE_TYPE 0x35 /* 53: */
#define DHCP_LEASE_TIME 0x33 /* 51: 32bit big-endian */
#define DHCP_OPTION_OVERLOAD 0x34 /* 52: 1 byte */
#define DHCP_MESSAGE_TYPE 0x35 /* 53: 1 byte */
#define DHCP_SERVER_ID 0x36 /* 54: server's IP */
#define DHCP_PARAM_REQ 0x37 /* 55: list of options client wants */
//#define DHCP_ERR_MESSAGE 0x38 /* 56: error message when sending NAK etc */
#define DHCP_MAX_SIZE 0x39 /* 57: */
#define DHCP_MAX_SIZE 0x39 /* 57: 16bit big-endian */
// 0x3a /* 58: from server: renew time, 32bit big-endian */
// 0x3b /* 59: from server: rebind time, 32bit big-endian */
#define DHCP_VENDOR 0x3c /* 60: client's vendor (a string) */
#define DHCP_CLIENT_ID 0x3d /* 61: by default client's MAC addr, but may be arbitrarily long */
//#define DHCP_TFTP_SERVER_NAME 0x42 /* 66: same as 'sname' field */
//#define DHCP_BOOT_FILE 0x43 /* 67: same as 'file' field */
//#define DHCP_USER_CLASS 0x4d /* 77: RFC 3004. set of LASCII strings. "I am a printer" etc */
// 0x50 /* 80: rapid commit ("I'm ok with getting immediate ACK, not just OFFER"), 0 bytes */
#define DHCP_FQDN 0x51 /* 81: client asks to update DNS to map its FQDN to its new IP */
//#define DHCP_PCODE 0x64 /* 100: RFC 4833. IEEE 1003.1 TZ string */
//#define DHCP_TCODE 0x65 /* 101: RFC 4833. Reference to the TZ database string */