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[176.103.220.4]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49d1fd532dcsm122867485e9.1.2026.09.10.07.51.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 10 Sep 2026 07:51:11 -0700 (PDT) From: Stefano Brivio To: Anshu Kumari Subject: Re: [PATCH v3 1/2] dhcpv6: Add --dhcpv6-opt with option type table and value parser Message-ID: <20260910165109.39277281@elisabeth> In-Reply-To: <20260824121352.244081-2-anskuma@redhat.com> References: <20260824121352.244081-1-anskuma@redhat.com> <20260824121352.244081-2-anskuma@redhat.com> Organization: Red Hat X-Mailer: Claws Mail 4.2.0 (GTK 3.24.49; x86_64-pc-linux-gnu) MIME-Version: 1.0 Date: Thu, 10 Sep 2026 16:51:10 +0200 (CEST) X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: x2p7zjMGaxu8qfAnG7vMlroRHDH88oCA3Wq7hRFfzJk_1789051874 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Message-ID-Hash: FX7OGDTJ3IMOYE6RY64NZCQXT3WGVB2V X-Message-ID-Hash: FX7OGDTJ3IMOYE6RY64NZCQXT3WGVB2V X-MailFrom: sbrivio@redhat.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: passt-dev@passt.top, david@gibson.dropbear.id.au, jmaloy@redhat.com, lvivier@redhat.com X-Mailman-Version: 3.3.8 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On Mon, 24 Aug 2026 17:43:51 +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 > --- > v3: > - Use parse_unsigned(), parse_literal(), parse_eoi() from parse.c > instead of manual strtoul()/errno/strchr() in dhcpv6_opt_parse() > for UINT and VENDOR_CLASS cases. > - Store options as pre-parsed binary in a static array indexed by > option code, instead of storing raw strings. > - Add dhcpv6_opt_to_str() to render binary option values back to > printable strings for startup logging in conf_print(). > > 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 | 25 ++++- > dhcpv6.c | 326 ++++++++++++++++++++++++++++++++++++++++++++++++++++++- > dhcpv6.h | 2 + > passt.1 | 31 ++++++ > 4 files changed, 382 insertions(+), 2 deletions(-) > > diff --git a/conf.c b/conf.c > index faf2681..17c7c0c 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" > @@ -632,7 +633,8 @@ 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 > @@ -900,6 +902,9 @@ 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 = 1; i < UINT16_MAX; i++) Curly brackets (not because they're needed, just for coding style). > + if (dhcpv6_opt_to_str(i, buf, sizeof(buf))) > + info(" option %u: %s", i, buf); > > dns6: > for (i = 0; i < ARRAY_SIZE(c->ip6.dns); i++) { > @@ -1348,6 +1353,7 @@ void conf(struct ctx *c, int argc, char **argv) > {"stats", required_argument, NULL, 31 }, > {"conf-path", required_argument, NULL, 'c' }, > {"chroot-fallback", no_argument, NULL, 32 }, > + {"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:"; > @@ -1589,6 +1595,23 @@ void conf(struct ctx *c, int argc, char **argv) > case 32: > c->chroot_fallback = true; > break; > + case 35: { > + unsigned long dhcpv6_opt_code; > + p = optarg; > + > + if (!parse_unsigned(&p, 0, &dhcpv6_opt_code) || > + !parse_literal(&p, ",")) { Conversely, not needed here. > + die("--dhcpv6-opt requires CODE,VALUE format"); > + } > + > + if (dhcpv6_opt_code < 1) { > + die("Invalid DHCPv6 option code: %s", > + optarg); This fits on a single line now (and curly brackets could go away). > + } > + > + dhcpv6_set_opt(dhcpv6_opt_code, p); > + break; > + } > case 'd': > c->debug = 1; > c->quiet = 0; > diff --git a/dhcpv6.c b/dhcpv6.c > index 29c7e32..3964dd9 100644 > --- a/dhcpv6.c > +++ b/dhcpv6.c > @@ -25,12 +25,15 @@ > #include > #include > #include > +#include > > #include "packet.h" > #include "util.h" > #include "passt.h" > #include "tap.h" > #include "log.h" > +#include "inany.h" > +#include "parse.h" > > /** > * struct opt_hdr - DHCPv6 option header > @@ -278,6 +281,328 @@ 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_UINT8: Unsigned 8-bit integer > + * @DHCPV6_OPT_UINT16: Unsigned 16-bit integer > + * @DHCPV6_OPT_UINT32: 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_UINT8, > + DHCPV6_OPT_UINT16, > + DHCPV6_OPT_UINT32, > + 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_UINT8, /* 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_UINT32, /* Information Refresh Time */ > + [59] = DHCPV6_OPT_STR, /* Boot File URL */ > + [60] = DHCPV6_OPT_LEN_STR_LIST, /* Boot File Params */ > + [82] = DHCPV6_OPT_UINT32, /* SOL_MAX_RT */ > + [83] = DHCPV6_OPT_UINT32, /* 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 > + */ > +static 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; > + uint8_t width; > + size_t slen; > + int len; > + > + if (!*str) > + return -1; > + > + if (code >= ARRAY_SIZE(dhcpv6_opt_types)) > + return -1; > + > + type = dhcpv6_opt_types[code]; > + > + switch (type) { > + case DHCPV6_OPT_NONE: > + return -1; > + case DHCPV6_OPT_IPV6: > + case DHCPV6_OPT_IPV6_LIST: { We usually try to avoid blocks to workaround warnings about mixing declarations and code, unless it's really necessary. Here 'addr' and 'af' could be happily declared a few lines above. > + union inany_addr addr; > + sa_family_t af; > + > + len = 0; > + > + do { > + if (len + sizeof(struct in6_addr) > buf_len) > + return -1; > + > + if (!parse_inany_(&str, &addr, &af) || > + af != AF_INET6) This fits on one line now. > + return -1; > + > + memcpy(buf + len, &addr.a6, sizeof(struct in6_addr)); > + len += sizeof(struct in6_addr); > + > + if (type == DHCPV6_OPT_IPV6) > + break; > + } while (parse_literal(&str, ",")); > + > + if (!len || !parse_eoi(str)) > + return -1; > + > + return len; > + } > + case DHCPV6_OPT_UINT8: > + case DHCPV6_OPT_UINT16: > + case DHCPV6_OPT_UINT32: > + if (type == DHCPV6_OPT_UINT8) > + width = 1; > + else if (type == DHCPV6_OPT_UINT16) > + width = 2; > + else > + width = 4; > + > + if (buf_len < width) > + return -1; > + > + if (!parse_unsigned(&str, 0, &val) || > + !parse_eoi(str) || This too. > + val >= (1ULL << (width * 8))) > + return -1; > + > + if (type == DHCPV6_OPT_UINT16) > + *(uint16_t *)buf = htons(val); > + else if (type == DHCPV6_OPT_UINT32) > + *(uint32_t *)buf = htonl(val); > + else > + buf[0] = val; > + > + 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: { > + uint16_t slen_net; > + uint32_t ent; > + > + if (!parse_unsigned(&str, 0, &val) || > + !parse_literal(&str, ":") || This too. > + val > UINT32_MAX) > + return -1; > + > + slen = strlen(str); > + 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)); > + > + slen_net = htons(slen); > + memcpy(buf + sizeof(uint32_t), &slen_net, sizeof(slen_net)); > + > + memcpy(buf + sizeof(uint32_t) + sizeof(uint16_t), > + str, slen); This too. > + > + return len; > + } > + case DHCPV6_OPT_LEN_STR_LIST: > + len = 0; > + > + while (*str) { > + uint16_t slen_net; > + > + slen = strcspn(str, ","); > + if (!slen) > + return -1; > + > + if (len + (int)(sizeof(uint16_t) + slen) > (int)buf_len) > + return -1; > + > + slen_net = htons(slen); > + memcpy(buf + len, &slen_net, sizeof(slen_net)); > + len += sizeof(uint16_t); > + > + memcpy(buf + len, str, slen); > + len += slen; > + > + str += slen; > + if (*str == ',') > + str++; > + } > + > + if (!len) > + return -1; > + > + return len; > + } > + > + return -1; > +} > + > +/** > + * struct dhcpv6_user_opts - User-specified DHCPv6 options from --dhcpv6-opt > + * @val: Binary option value in wire format > + * @len: Length of @val in bytes, 0 if not set > + */ > +static struct { > + uint8_t val[UINT16_MAX]; > + int len; > +} dhcpv6_user_opts[ARRAY_SIZE(dhcpv6_opt_types)]; > + > +/** > + * dhcpv6_opt_to_str() - Render a binary DHCPv6 option value to printable string > + * @code: DHCPv6 option code > + * @buf: Output string buffer > + * @buf_len: Size of output buffer > + * > + * Return: pointer to @buf if option is set, NULL otherwise > + */ > +const char *dhcpv6_opt_to_str(uint16_t code, char *buf, size_t buf_len) > +{ > + enum dhcpv6_opt_type type; > + unsigned int i; > + uint16_t slen; > + int off = 0; > + > + if (code >= ARRAY_SIZE(dhcpv6_user_opts) || > + !dhcpv6_user_opts[code].len) This should be aligned under the ( above (just after it). By the way I think it's a good example of why we do that: at a glance, it seems to be on the same logic level as "return NULL;" otherwise. > + return NULL; > + > + type = dhcpv6_opt_types[code]; > + > + switch (type) { > + case DHCPV6_OPT_IPV6: > + case DHCPV6_OPT_IPV6_LIST: > + for (i = 0; i + sizeof(struct in6_addr) <= > + (unsigned int)dhcpv6_user_opts[code].len; > + i += sizeof(struct in6_addr)) { This would be good to have as an iterator macro (see my comment to the DHCP series). > + if (off) > + off += snprintf(buf + off, buf_len - off, ","); > + inet_ntop(AF_INET6, dhcpv6_user_opts[code].val + i, > + buf + off, buf_len - off); > + off = strlen(buf); > + } > + return buf; > + case DHCPV6_OPT_UINT8: > + case DHCPV6_OPT_UINT16: > + case DHCPV6_OPT_UINT32: { > + unsigned int val = 0; > + int j; > + > + for (j = 0; j < dhcpv6_user_opts[code].len; j++) > + val = (val << 8) | dhcpv6_user_opts[code].val[j]; > + > + (void)snprintf(buf, buf_len, "%u", val); > + return buf; > + } > + case DHCPV6_OPT_STR: > + (void)snprintf(buf, buf_len, "%.*s", > + dhcpv6_user_opts[code].len, > + dhcpv6_user_opts[code].val); This should all be aligned after the ( from snprintf(). > + return buf; > + case DHCPV6_OPT_VENDOR_CLASS: { > + uint32_t ent; > + int doff; > + > + if (dhcpv6_user_opts[code].len < > + (int)(sizeof(uint32_t) + sizeof(uint16_t))) > + return NULL; > + > + memcpy(&ent, dhcpv6_user_opts[code].val, sizeof(ent)); > + memcpy(&slen, dhcpv6_user_opts[code].val + sizeof(uint32_t), > + sizeof(slen)); > + doff = sizeof(uint32_t) + sizeof(uint16_t); > + > + (void)snprintf(buf, buf_len, "%u:%.*s", > + ntohl(ent), ntohs(slen), > + dhcpv6_user_opts[code].val + doff); > + return buf; > + } > + case DHCPV6_OPT_LEN_STR_LIST: > + off = 0; > + i = 0; > + > + while (i + sizeof(uint16_t) <= > + (unsigned int)dhcpv6_user_opts[code].len) { > + memcpy(&slen, dhcpv6_user_opts[code].val + i, > + sizeof(slen)); > + slen = ntohs(slen); > + i += sizeof(uint16_t); > + > + if (i + slen > (unsigned int)dhcpv6_user_opts[code].len) > + break; > + > + if (off) > + off += snprintf(buf + off, buf_len - off, ","); > + off += snprintf(buf + off, buf_len - off, "%.*s", > + slen, dhcpv6_user_opts[code].val + i); > + i += slen; > + } > + return buf; > + default: > + return NULL; > + } > +} > + > +/** > + * dhcpv6_set_opt() - Parse and store a user-specified DHCPv6 option > + * @code: DHCPv6 option code > + * @val_str: Value string from command line > + */ > +void dhcpv6_set_opt(uint16_t code, const char *val_str) > +{ > + int ret; > + > + if (code >= ARRAY_SIZE(dhcpv6_user_opts)) > + die("DHCPv6 option code %u out of supported range", code); > + > + ret = dhcpv6_opt_parse(code, val_str, > + dhcpv6_user_opts[code].val, > + sizeof(dhcpv6_user_opts[code].val)); > + if (ret < 0) > + die("Invalid value for DHCPv6 option %u: %s", code, val_str); > + > + dhcpv6_user_opts[code].len = ret; > +} > + > /** > * dhcpv6_opt() - Get option from DHCPv6 message > * @data: Buffer with options, set to matching option on return > @@ -678,7 +1003,6 @@ int dhcpv6(struct ctx *c, struct iov_tail *data, > sizeof(struct opt_hdr) + ntohs(client_id->l); > n = dhcpv6_dns_fill(c, (char *)&resp, n); > n = dhcpv6_client_fqdn_fill(data, c, (char *)&resp, n); > - > resp.hdr.xid = mh->xid; > > tap_udp6_send(c, src, 547, saddr, 546, mh->xid, &resp, n); > diff --git a/dhcpv6.h b/dhcpv6.h > index 1015a1a..973c477 100644 > --- a/dhcpv6.h > +++ b/dhcpv6.h > @@ -9,5 +9,7 @@ > int dhcpv6(struct ctx *c, struct iov_tail *data, > const struct in6_addr *saddr, const struct in6_addr *daddr); > void dhcpv6_init(const struct ctx *c); > +void dhcpv6_set_opt(uint16_t code, const char *val_str); > +const char *dhcpv6_opt_to_str(uint16_t code, char *buf, size_t buf_len); > > #endif /* DHCPV6_H */ > diff --git a/passt.1 b/passt.1 > index 53e072a..156aa8d 100644 > --- a/passt.1 > +++ b/passt.1 > @@ -440,6 +440,37 @@ 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 either: -- Stefano