8aa626fff
Denys Vlasenko
2021-09-04
Subject
udhcp: add comments, no code changes
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networking/udhcp/common.h+24 -7
| @@ -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 */ | |