diff options
| -rw-r--r-- | dhcp.c | 93 |
1 files changed, 69 insertions, 24 deletions
@@ -67,6 +67,12 @@ struct opt { static struct opt opts[256]; +#define foreach_opt(o) for ((o) = 0; (size_t)(o) < ARRAY_SIZE(opts); (o)++) + +#define foreach_unsent_opt(o) \ + foreach_opt((o)) \ + if (opts[(o)].conf != OPT_UNSET && !opts[(o)].sent) + #define DHCPDISCOVER 1 #define DHCPOFFER 2 #define DHCPREQUEST 3 @@ -419,16 +425,14 @@ const char *dhcp_opt_to_str(uint8_t code, char *buf, size_t buf_len) * @size: Usable size of @buf (excluding end marker) * @o: Option number * @offset: Current offset within @buf, updated on insertion - * - * Return: false if @buf has space to write the option, true otherwise */ -static bool fill_one(uint8_t *buf, size_t size, int o, int *offset) +static void fill_one(uint8_t *buf, size_t size, int o, int *offset) { size_t slen = opts[o].slen; /* If we don't have space to write the option, then just skip */ if (*offset + 2 /* code and length of option */ + slen > size) - return true; + return; buf[*offset] = o; buf[*offset + 1] = slen; @@ -440,17 +444,33 @@ static bool fill_one(uint8_t *buf, size_t size, int o, int *offset) opts[o].sent = 1; *offset += slen; - return false; } /** - * fill() - Fill options in message - * @m: Message to fill + * enum dhcp_overload - DHCP option overload values (RFC 2132, Section 9.3) + * @DHCP_OVERLOAD_NONE: No overload + * @DHCP_OVERLOAD_FILE: file field carries options + * @DHCP_OVERLOAD_SNAME: sname field carries options + */ +enum dhcp_overload { + DHCP_OVERLOAD_NONE = 0, + DHCP_OVERLOAD_FILE = 1, + DHCP_OVERLOAD_SNAME = 2, +}; + +/** + * fill() - Fill options in message, with overload into file/sname if needed + * @m: Message to fill + * @has_bootfile: Reserve file field for boot file name * * Return: current size of options field */ -static int fill(struct msg *m) +static int fill(struct msg *m, bool has_bootfile) { + enum dhcp_overload overload = DHCP_OVERLOAD_NONE; + int sname_off = 0, file_off = 0; + /* Reserve 3 bytes for option 52 (overload) if needed */ + size_t size = OPT_MAX - 3; int i, o, offset = 0; for (o = 0; o < 255; o++) @@ -460,24 +480,47 @@ static int fill(struct msg *m) * option 53 at the beginning of the list. * Put it there explicitly, unless requested via option 55. */ - if (opts[55].clen > 0 && !memchr(opts[55].c, 53, opts[55].clen)) { - if (fill_one(m->o, OPT_MAX, 53, &offset)) - debug("DHCP: skipping option 53"); - } + if (opts[55].clen > 0 && !memchr(opts[55].c, 53, opts[55].clen)) + fill_one(m->o, size, 53, &offset); for (i = 0; i < opts[55].clen; i++) { o = opts[55].c[i]; - if (opts[o].conf != OPT_UNSET) { - if (fill_one(m->o, OPT_MAX, o, &offset)) - debug("DHCP: skipping option %i", o); - } + if (opts[o].conf != OPT_UNSET) + fill_one(m->o, size, o, &offset); } for (o = 0; o < 255; o++) { - if (opts[o].conf != OPT_UNSET && !opts[o].sent) { - if (fill_one(m->o, OPT_MAX, o, &offset)) - debug("DHCP: skipping option %i", o); - } + if (opts[o].conf != OPT_UNSET && !opts[o].sent) + fill_one(m->o, size, o, &offset); + } + + /* Overflow unsent options into sname, then file */ + foreach_unsent_opt(o) + fill_one(m->sname, sizeof(m->sname) - 1, o, &sname_off); + + if (!has_bootfile) { + foreach_unsent_opt(o) + fill_one(m->file, sizeof(m->file) - 1, o, &file_off); + } + + /* Report any options that could not be sent */ + foreach_unsent_opt(o) + debug("DHCP: skipping option %i", o); + + if (sname_off) { + m->sname[sname_off] = 255; + overload |= DHCP_OVERLOAD_SNAME; + } + + if (file_off) { + m->file[file_off] = 255; + overload |= DHCP_OVERLOAD_FILE; + } + + if (overload) { + m->o[offset++] = 52; + m->o[offset++] = 1; + m->o[offset++] = overload; } m->o[offset++] = 255; @@ -770,16 +813,18 @@ int dhcp(const struct ctx *c, struct iov_tail *data) } } - if (!c->no_dhcp_dns_search) - opt_set_dns_search(c, sizeof(m->o)); + if (!c->no_dhcp_dns_search) { + /* 3 bytes reserved for option 52 (code, length, value) */ + opt_set_dns_search(c, OPT_MAX - 3); + } /* RFC 2132, Section 9.5: put boot file name in the 'file' header - * field. + * field. Reserve the file field from overload. */ has_bootfile = opts[67].slen > 0 && (size_t)opts[67].slen < sizeof(reply.file); - dlen = offsetof(struct msg, o) + fill(&reply); + dlen = offsetof(struct msg, o) + fill(&reply, has_bootfile); if (has_bootfile) memcpy(reply.file, opts[67].s, opts[67].slen); |