On Thu, Jun 18, 2026 at 05:35:28PM +0530, Anshu Kumari wrote: > Introduce the --dhcpv6-opt flag that allows setting arbitrary DHCPv6 > options from command-line in the form [--dhcpv6-opt CODE,VALUE]. > > Add a type lookup table mapping option codes to value types (IPv6, > IPv6 list, integer, string, vendor class, length-prefixed string > list) and dhcpv6_opt_parse() to convert CLI strings to binary wire > format. If the same option code is given more than once, the > last value wins. > > Link: https://bugs.passt.top/show_bug.cgi?id=192 > Signed-off-by: Anshu Kumari > --- > v2: > - Renamed custom_v6opts to dhcpv6_opts, MAX_CUSTOM_DHCPV6_OPTS > to MAX_DHCPV6_OPTS. > - Dropped val/len from ctx struct. > - Moved dhcpv6_add_option() to conf.c as static > conf_dhcpv6_option(). > - Made dhcpv6_opt_parse() non-static, declared in dhcpv6.h > - Omitted explicit [256] from dhcpv6_opt_types[]. > - Moved chunk declaration into while block. > - Removed redundant !slen check in DHCPV6_OPT_STR case. > - All errors in dhcpv6_opt_parse() return -1, removed die() > calls. > --- > conf.c | 60 +++++++++++++++- > dhcpv6.c | 209 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ > dhcpv6.h | 2 + > passt.1 | 31 +++++++++ > passt.h | 12 ++++ > 5 files changed, 313 insertions(+), 1 deletion(-) > > diff --git a/conf.c b/conf.c > index cd05adf..3981c1b 100644 > --- a/conf.c > +++ b/conf.c > @@ -47,6 +47,7 @@ > #include "lineread.h" > #include "isolation.h" > #include "log.h" > +#include "dhcpv6.h" > #include "vhost_user.h" > #include "epoll_ctl.h" > #include "conf.h" > @@ -616,7 +617,8 @@ static void usage(const char *name, FILE *f, int status) > " -S, --search LIST Space-separated list, search domains\n" > " a single, empty option disables the DNS search list\n" > " -H, --hostname NAME Hostname to configure client with\n" > - " --fqdn NAME FQDN to configure client with\n"); > + " --fqdn NAME FQDN to configure client with\n" > + " --dhcpv6-opt CODE,VAL Set DHCPv6 option CODE to VAL\n"); > if (strstr(name, "pasta")) > FPRINTF(f, " default: don't use any search list\n"); > else > @@ -884,6 +886,10 @@ static void conf_print(const struct ctx *c) > info(" our link-local: %s", > inet_ntop(AF_INET6, &c->ip6.our_tap_ll, > buf, sizeof(buf))); > + for (i = 0; i < c->dhcpv6_opts_count; i++) > + info(" v6 option %u: %s", > + c->dhcpv6_opts[i].code, > + c->dhcpv6_opts[i].str); > > dns6: > for (i = 0; i < ARRAY_SIZE(c->ip6.dns); i++) { > @@ -1150,6 +1156,41 @@ static void conf_sock_listen(const struct ctx *c) > die_perror("Couldn't add configuration socket to epoll"); > } > > +/** > + * conf_dhcpv6_option() - Set value for a DHCPv6 option in configuration > + * @c: Execution context > + * @code: DHCPv6 option code > + * @val_str: Value string from command line > + */ > +static void conf_dhcpv6_option(struct ctx *c, uint16_t code, > + const char *val_str) > +{ > + uint8_t tmp[255]; > + int idx; > + > + if (dhcpv6_opt_parse(code, val_str, tmp, sizeof(tmp)) < 0) > + die("Invalid value for DHCPv6 option %u: %s", code, val_str); As for DHCPv4, I wonder if we can avoid double parsing each option. I realise the data structures in dhcpv6.c are different from those in dhcp.c, so it might not reasonable here, even if it is there. > + for (idx = 0; idx < c->dhcpv6_opts_count; idx++) { > + if (c->dhcpv6_opts[idx].code == code) > + break; > + } > + > + if (idx == c->dhcpv6_opts_count) { > + if (c->dhcpv6_opts_count >= MAX_DHCPV6_OPTS) > + die("Too many --dhcpv6-opt entries (max %d)", > + MAX_DHCPV6_OPTS); > + c->dhcpv6_opts_count++; > + } > + > + c->dhcpv6_opts[idx].code = code; > + > + if (snprintf_check(c->dhcpv6_opts[idx].str, > + sizeof(c->dhcpv6_opts[0].str), > + "%s", val_str)) > + die("DHCPv6 option value too long: %s", val_str); > +} > + > /** > * conf() - Process command-line arguments and set configuration > * @c: Execution context > @@ -1233,6 +1274,7 @@ void conf(struct ctx *c, int argc, char **argv) > {"migrate-no-linger", no_argument, NULL, 30 }, > {"stats", required_argument, NULL, 31 }, > {"conf-path", required_argument, NULL, 'c' }, > + {"dhcpv6-opt", required_argument, NULL, 35 }, > { 0 }, > }; > const char *optstring = "+dqfel:hs:c:F:I:p:P:m:a:n:M:g:i:o:D:S:H:461t:u:T:U:"; > @@ -1248,10 +1290,13 @@ void conf(struct ctx *c, int argc, char **argv) > uint8_t prefix_len_from_opt = 0; > unsigned int ifi4 = 0, ifi6 = 0; > const char *logfile = NULL; > + unsigned long v6optcode; > char *runas = NULL; > size_t logsize = 0; > + const char *comma; > long fd_tap_opt; > int name, ret; > + char *end; > uid_t uid; > gid_t gid; > > @@ -1467,6 +1512,19 @@ void conf(struct ctx *c, int argc, char **argv) > die("Can't display statistics if not running in foreground"); > c->stats = strtol(optarg, NULL, 0); > break; > + case 35: > + comma = strchr(optarg, ','); > + if (!comma) > + die("--dhcpv6-opt requires CODE,VALUE format"); > + > + errno = 0; > + v6optcode = strtoul(optarg, &end, 0); > + if (end != comma || errno || v6optcode < 1) > + die("Invalid DHCPv6 option code: %s", > + optarg); > + > + conf_dhcpv6_option(c, v6optcode, comma + 1); > + break; > case 'd': > c->debug = 1; > c->quiet = 0; > diff --git a/dhcpv6.c b/dhcpv6.c > index 97c04e2..1e1dd0d 100644 > --- a/dhcpv6.c > +++ b/dhcpv6.c > @@ -25,6 +25,7 @@ > #include > #include > #include > +#include > > #include "packet.h" > #include "util.h" > @@ -278,6 +279,214 @@ static struct resp_not_on_link_t { > { 0, }, > }; > > +/** > + * enum dhcpv6_opt_type - DHCPv6 option value types > + * @DHCPV6_OPT_NONE: Unsupported or unknown option > + * @DHCPV6_OPT_STR: Variable-length string > + * @DHCPV6_OPT_IPV6: Single IPv6 address > + * @DHCPV6_OPT_IPV6_LIST: Multiple IPv6 addresses, comma-separated > + * @DHCPV6_OPT_INT8: Unsigned 8-bit integer > + * @DHCPV6_OPT_INT16: Unsigned 16-bit integer > + * @DHCPV6_OPT_INT32: Unsigned 32-bit integer > + * @DHCPV6_OPT_VENDOR_CLASS: Enterprise number + length-prefixed data > + * @DHCPV6_OPT_LEN_STR_LIST: Length-prefixed string list > + */ > +enum dhcpv6_opt_type { > + DHCPV6_OPT_NONE, > + DHCPV6_OPT_STR, > + DHCPV6_OPT_IPV6, > + DHCPV6_OPT_IPV6_LIST, > + DHCPV6_OPT_INT8, > + DHCPV6_OPT_INT16, > + DHCPV6_OPT_INT32, > + DHCPV6_OPT_VENDOR_CLASS, > + DHCPV6_OPT_LEN_STR_LIST, > +}; > + > +/** > + * dhcpv6_opt_types - Maps DHCPv6 option code to value type, indexed by code > + * RFC 8415 Options: 7, 15, 16, 17, 32, 82, 83 > + * RFC 5970 Options: 59, 60 > + * RFC 4075 Options: 31 > + */ > +static const enum dhcpv6_opt_type dhcpv6_opt_types[] = { > + [7] = DHCPV6_OPT_INT8, /* Preference */ > + [15] = DHCPV6_OPT_LEN_STR_LIST, /* User Class */ > + [16] = DHCPV6_OPT_VENDOR_CLASS, /* Vendor Class */ > + [17] = DHCPV6_OPT_VENDOR_CLASS, /* Vendor Opts */ > + [31] = DHCPV6_OPT_IPV6_LIST, /* SNTP Servers */ > + [32] = DHCPV6_OPT_INT32, /* Information Refresh Time */ > + [59] = DHCPV6_OPT_STR, /* Boot File URL */ > + [60] = DHCPV6_OPT_LEN_STR_LIST, /* Boot File Params */ > + [82] = DHCPV6_OPT_INT32, /* SOL_MAX_RT */ > + [83] = DHCPV6_OPT_INT32, /* INF_MAX_RT */ > +}; > + > +/** > + * dhcpv6_opt_parse() - Parse a DHCPv6 option value string into binary > + * @code: DHCPv6 option code > + * @str: Value string from command line > + * @buf: Output buffer for binary value > + * @buf_len: Size of output buffer > + * > + * Return: number of bytes written to @buf, or -1 on error > + */ > +int dhcpv6_opt_parse(uint16_t code, const char *str, > + uint8_t *buf, size_t buf_len) > +{ > + enum dhcpv6_opt_type type; > + unsigned long val; > + unsigned int i; > + uint8_t width; > + size_t slen; > + char *end; > + int len; > + > + if (!*str) > + return -1; > + > + if (code >= ARRAY_SIZE(dhcpv6_opt_types)) > + return -1; > + > + type = dhcpv6_opt_types[code]; > + > + switch (type) { A number of these types result in identical parsing to DHCPv4. Could we have a unified parser function? Obviously things like IPv4 address and IPv6 address would need different types, but we should be able to share at least the integer and string code. > + case DHCPV6_OPT_NONE: > + return -1; > + case DHCPV6_OPT_IPV6: > + case DHCPV6_OPT_IPV6_LIST: > + len = 0; > + > + while (*str) { > + char chunk[INET6_ADDRSTRLEN]; > + size_t clen; > + > + clen = strcspn(str, ","); > + if (!clen || clen >= sizeof(chunk)) > + return -1; > + > + if (len + (int)sizeof(struct in6_addr) > (int)buf_len) > + return -1; > + > + memcpy(chunk, str, clen); > + chunk[clen] = '\0'; > + > + if (inet_pton(AF_INET6, chunk, buf + len) != 1) > + return -1; > + > + len += sizeof(struct in6_addr); > + > + if (type == DHCPV6_OPT_IPV6) { > + if (str[clen] == ',') > + return -1; > + break; > + } > + > + str += clen + (str[clen] == ','); > + } > + > + if (!len) > + return -1; > + > + return len; > + case DHCPV6_OPT_INT8: > + case DHCPV6_OPT_INT16: > + case DHCPV6_OPT_INT32: > + if (type == DHCPV6_OPT_INT8) > + width = 1; > + else if (type == DHCPV6_OPT_INT16) > + width = 2; > + else > + width = 4; > + > + if (buf_len < width) > + return -1; > + > + errno = 0; > + val = strtoul(str, &end, 0); > + > + if (*end || errno || val >= (1ULL << (width * 8))) > + return -1; > + > + for (i = width; i > 0; i--) { > + buf[i - 1] = val & 0xff; > + val >>= 8; > + } > + > + return width; > + case DHCPV6_OPT_STR: > + slen = strlen(str); > + > + if (slen >= buf_len) > + return -1; > + > + memcpy(buf, str, slen); > + > + return slen; > + case DHCPV6_OPT_VENDOR_CLASS: { > + const char *colon; > + uint32_t ent; > + > + colon = strchr(str, ':'); > + if (!colon) > + return -1; > + > + errno = 0; > + val = strtoul(str, &end, 0); > + if (end != colon || errno || val > UINT32_MAX) > + return -1; > + > + slen = strlen(colon + 1); > + if (!slen) > + return -1; > + > + len = sizeof(uint32_t) + sizeof(uint16_t) + slen; > + if ((size_t)len > buf_len) > + return -1; > + > + ent = htonl(val); > + memcpy(buf, &ent, sizeof(ent)); > + > + buf[4] = slen >> 8; > + buf[5] = slen & 0xff; > + > + memcpy(buf + sizeof(uint32_t) + sizeof(uint16_t), > + colon + 1, slen); > + > + return len; > + } > + case DHCPV6_OPT_LEN_STR_LIST: > + len = 0; > + > + while (*str) { > + slen = strcspn(str, ","); > + if (!slen) > + return -1; > + > + if (len + (int)(sizeof(uint16_t) + slen) > (int)buf_len) > + return -1; > + > + buf[len] = slen >> 8; > + buf[len + 1] = slen & 0xff; > + len += sizeof(uint16_t); > + > + memcpy(buf + len, str, slen); > + len += slen; > + > + str += slen; > + if (*str == ',') > + str++; > + } > + > + if (!len) > + return -1; > + > + return len; > + } > + > + return -1; > +} > + > /** > * dhcpv6_opt() - Get option from DHCPv6 message > * @data: Buffer with options, set to matching option on return > diff --git a/dhcpv6.h b/dhcpv6.h > index c706dfd..2da1c76 100644 > --- a/dhcpv6.h > +++ b/dhcpv6.h > @@ -9,5 +9,7 @@ > int dhcpv6(struct ctx *c, struct iov_tail *data, > struct in6_addr *saddr, struct in6_addr *daddr); > void dhcpv6_init(const struct ctx *c); > +int dhcpv6_opt_parse(uint16_t code, const char *str, > + uint8_t *buf, size_t buf_len); > > #endif /* DHCPV6_H */ > diff --git a/passt.1 b/passt.1 > index 908fd4a..0f771cb 100644 > --- a/passt.1 > +++ b/passt.1 > @@ -430,6 +430,37 @@ Send \fIname\fR as DHCP option 12 (hostname). > FQDN to configure the client with. > Send \fIname\fR as Client FQDN: DHCP option 81 and DHCPv6 option 39. > > +.TP > +.BR \-\-dhcpv6-opt " " \fICODE\fR,\fIVALUE\fR > +Set DHCPv6 option \fICODE\fR to \fIVALUE\fR. The value format depends > +on the option type and is determined automatically from the option code. > +Multiple IPv6 addresses are comma-separated. > +This option can be specified multiple times. If the same option code is > +given more than once, the last value wins. > +.RS > +.TP > +.B String options > +59 (Boot File URL, RFC 5970) > +.TP > +.B Length-prefixed string list options (comma-separated entries) > +15 (User Class, RFC 8415), 60 (Boot File Params, RFC 5970). > +Each comma-separated entry is encoded with a 2-byte length prefix. > +Example: \fB\-\-dhcpv6-opt 15,class1,class2\fR. > +.TP > +.B Vendor class options (ENTERPRISE:DATA format) > +16 (Vendor Class, RFC 8415), 17 (Vendor-specific Info, RFC 8415). > +VALUE is \fIENTERPRISE\fR:\fIDATA\fR where \fIENTERPRISE\fR is the IANA > +Private Enterprise Number and \fIDATA\fR is the vendor class string. > +Example: \fB\-\-dhcpv6-opt 16,0:HTTPClient\fR for UEFI HTTP Boot. > +.TP > +.B IPv6 address list options (comma-separated) > +31 (SNTP Servers) > +.TP > +.B Integer options > +7 (Preference, 8-bit), 32 (Information Refresh Time, 32-bit), > +82 (SOL_MAX_RT, 32-bit), 83 (INF_MAX_RT, 32-bit) > +.RE > + > .TP > .BR \-t ", " \-\-tcp-ports " " \fIspec > Configure TCP port forwarding to guest or namespace. \fIspec\fR can be one of: > diff --git a/passt.h b/passt.h > index 3a07294..8f4ddef 100644 > --- a/passt.h > +++ b/passt.h > @@ -182,6 +182,10 @@ struct ip6_ctx { > * @dns_search: DNS search list > * @hostname: Guest hostname > * @fqdn: Guest FQDN > + * @dhcpv6_opts: User-specified DHCPv6 options from --dhcpv6-opt > + * @dhcpv6_opts.code: DHCPv6 option code > + * @dhcpv6_opts.str: String value from command line > + * @dhcpv6_opts_count: Number of entries in @dhcpv6_opts > * @ifi6: Template interface for IPv6, -1: none, 0: IPv6 disabled > * @ip6: IPv6 configuration > * @pasta_ifn: Name of namespace interface for pasta > @@ -264,6 +268,14 @@ struct ctx { > char hostname[PASST_MAXDNAME]; > char fqdn[PASST_MAXDNAME]; > > +#define MAX_DHCPV6_OPTS 32 > + > + struct { > + uint16_t code; > + char str[255]; > + } dhcpv6_opts[MAX_DHCPV6_OPTS]; > + int dhcpv6_opts_count; > + > int ifi6; > struct ip6_ctx ip6; > > -- > 2.54.0 > -- David Gibson (he or they) | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you, not the other way | around. http://www.ozlabs.org/~dgibson