From: David Gibson <david@gibson.dropbear.id.au>
To: Anshu Kumari <anskuma@redhat.com>
Cc: Laurent Vivier <lvivier@redhat.com>,
passt-dev@passt.top, sbrivio@redhat.com, jmaloy@redhat.com
Subject: Re: [PATCH v2 3/6] dhcp: Add option type table and value parser
Date: Thu, 28 May 2026 15:45:28 +1000 [thread overview]
Message-ID: <ahfWeGdLrNfbTS0N@zatzit> (raw)
In-Reply-To: <CADJNnVK5GCRXHZki1H3+u8V0pk=-s4U=YX-tqO9_L2Mj6eE6oQ@mail.gmail.com>
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On Thu, May 28, 2026 at 11:09:06AM +0530, Anshu Kumari wrote:
> On Tue, May 26, 2026 at 9:35 PM Laurent Vivier <lvivier@redhat.com> wrote:
>
> > On 5/26/26 14:31, Anshu Kumari wrote:
> > > Add an RFC 2132 type lookup table mapping DHCP option codes to their
> > > expected value formats, and a dhcp_opt_parse() function that converts
> > > CLI string values into their binary wire representation.
> > >
> > > Wire dhcp_opt_parse() into the --dhcp-opt handler so that values are
> > > validated and encoded at configuration time.
> > >
> > > Link: https://bugs.passt.top/show_bug.cgi?id=192
> > > Signed-off-by: Anshu Kumari <anskuma@redhat.com>
> > > ---
> > > v2:
> > > - Replaced struct lookup table + dhcp_opt_type_lookup() function with
> > flat dhcp_opt_types[256] array indexed by code.
> > > - Consolidated DHCP_OPT_UINT8/UINT16/UINT32 into single
> > DHCP_OPT_INTEGER with dhcp_opt_int_width[256] table.
> > > - Dropped DHCP_OPT_ROUTES / option 121 entirely.
> > > - Added kerneldoc for enum dhcp_opt_type values.
> > > - Removed curly braces from switch cases, declarations before switch.
> > > - Added newlines before return statements.
> > > - Changed IP list delimiter from space to comma (--dhcp-opt
> > 6,1.1.1.1,8.8.8.8).
> > > - Defined DHCP_OPT_PARSE_BUF constant for bare 1024.
> > > - Added len and val[255] fields to struct here (moved from patch 1).
> > > - Added kerneldoc for @custom_opts.len and @custom_opts.val.
> > > - Wired dhcp_opt_parse() into case 32 (--dhcp-boot) to populate
> > val/len.
> > > ---
> > > conf.c | 16 ++++++
> > > dhcp.c | 148 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> > > dhcp.h | 17 +++++++
> > > passt.h | 4 ++
> > > 4 files changed, 185 insertions(+)
> > >
> > > diff --git a/conf.c b/conf.c
> > > index ae8ee26..3a5f45d 100644
> > > --- a/conf.c
> > > +++ b/conf.c
> > > @@ -1266,6 +1266,7 @@ void conf(struct ctx *c, int argc, char **argv)
> > > char *end;
> > > uid_t uid;
> > > gid_t gid;
> > > + int len;
> >
> > I think you don't need to introduce len for --dhcp-opt as you already use
> > ret for --dhcp-boot
> > >
> > >
> > > if (c->mode == MODE_PASTA)
> > > @@ -1482,7 +1483,14 @@ void conf(struct ctx *c, int argc, char **argv)
> > > die("Too many DHCP options (max %d)",
> > > MAX_CUSTOM_DHCP_OPTS);
> > >
> > > + ret = dhcp_opt_parse(67, optarg,
> > > +
> > c->custom_opts[c->custom_opts_count].val,
> > > +
> > sizeof(c->custom_opts[0].val));
> > > + if (ret < 0)
> > > + die("Invalid boot file value: %s", optarg);
> > > +
> > > c->custom_opts[c->custom_opts_count].code = 67;
> > > + c->custom_opts[c->custom_opts_count].len = ret;
> > > if
> > (snprintf_check(c->custom_opts[c->custom_opts_count].str,
> > > sizeof(c->custom_opts[0].str),
> > > "%s", optarg))
> > > @@ -1503,7 +1511,15 @@ void conf(struct ctx *c, int argc, char **argv)
> > > die("Too many --dhcp-opt entries (max %d)",
> > > MAX_CUSTOM_DHCP_OPTS);
> > >
> > > + len = dhcp_opt_parse(optcode, comma + 1,
> > > +
> > c->custom_opts[c->custom_opts_count].val,
> > > +
> > sizeof(c->custom_opts[0].val));
> >
> > you can use "ret" here too
> >
> > > + if (len < 0)
> > > + die("Invalid value for DHCP option %lu:
> > %s",
> > > + optcode, comma + 1);
> > > +
> > > c->custom_opts[c->custom_opts_count].code =
> > optcode;
> > > + c->custom_opts[c->custom_opts_count].len = len;
> > > if
> > (snprintf_check(c->custom_opts[c->custom_opts_count].str,
> > > sizeof(c->custom_opts[0].str),
> > > "%s", comma + 1))
> > > diff --git a/dhcp.c b/dhcp.c
> > > index 1ff8cba..e1c95ad 100644
> > > --- a/dhcp.c
> > > +++ b/dhcp.c
> > > @@ -33,6 +33,154 @@
> > > #include "log.h"
> > > #include "dhcp.h"
> > >
> > > +/**
> > > + * dhcp_opt_types - Maps option code to RFC 2132 value type, indexed by
> > code
> > > + */
> > > +static const enum dhcp_opt_type dhcp_opt_types[256] = {
> > > + [1] = DHCP_OPT_IPV4, /* Subnet Mask */
> > > + [2] = DHCP_OPT_INTEGER, /* Time Offset */
> > > + [3] = DHCP_OPT_IPV4_LIST, /* Router */
> > > + [4] = DHCP_OPT_IPV4_LIST, /* Time Server */
> > > + [5] = DHCP_OPT_IPV4_LIST, /* Name Server */
> > > + [6] = DHCP_OPT_IPV4_LIST, /* Domain Name Server */
> > > + [7] = DHCP_OPT_IPV4_LIST, /* Log Server */
> > > + [8] = DHCP_OPT_IPV4_LIST, /* Cookie Server */
> > > + [9] = DHCP_OPT_IPV4_LIST, /* LPR Server */
> > > + [10] = DHCP_OPT_IPV4_LIST, /* Impress Server */
> > > + [11] = DHCP_OPT_IPV4_LIST, /* Resource Location Server */
> > > + [12] = DHCP_OPT_STR, /* Host Name */
> > > + [13] = DHCP_OPT_INTEGER, /* Boot File Size */
> > > + [15] = DHCP_OPT_STR, /* Domain Name */
> > > + [16] = DHCP_OPT_IPV4, /* Swap Server */
> > > + [17] = DHCP_OPT_STR, /* Root Path */
> > > + [19] = DHCP_OPT_INTEGER, /* IP Forwarding */
> > > + [23] = DHCP_OPT_INTEGER, /* Default IP TTL */
> > > + [26] = DHCP_OPT_INTEGER, /* Interface MTU */
> > > + [28] = DHCP_OPT_IPV4, /* Broadcast Address */
> > > + [33] = DHCP_OPT_IPV4_LIST, /* Static Routes */
> > > + [37] = DHCP_OPT_INTEGER, /* TCP Default TTL */
> > > + [38] = DHCP_OPT_INTEGER, /* TCP Keepalive Interval */
> > > + [40] = DHCP_OPT_STR, /* NIS Domain Name */
> > > + [41] = DHCP_OPT_IPV4_LIST, /* NIS Servers */
> > > + [42] = DHCP_OPT_IPV4_LIST, /* NTP Servers */
> > > + [44] = DHCP_OPT_IPV4_LIST, /* NetBIOS Name Server */
> > > + [50] = DHCP_OPT_IPV4, /* Requested IP Address */
> > > + [51] = DHCP_OPT_INTEGER, /* IP Address Lease Time */
> > > + [53] = DHCP_OPT_INTEGER, /* DHCP Message Type */
> > > + [54] = DHCP_OPT_IPV4, /* Server Identifier */
> > > + [55] = DHCP_OPT_STR, /* Parameter Request List */
> >
> > This is a client option, I don't think we need to manage it.
> >
> > > + [57] = DHCP_OPT_INTEGER, /* Max DHCP Message Size */
> > > + [58] = DHCP_OPT_INTEGER, /* Renewal (T1) Time */
> > > + [59] = DHCP_OPT_INTEGER, /* Rebinding (T2) Time */
> > > + [60] = DHCP_OPT_STR, /* Vendor Class Identifier */
> > > + [61] = DHCP_OPT_STR, /* Client Identifier */
> >
> > This is also a client option.
> >
> > > + [66] = DHCP_OPT_STR, /* TFTP Server Name */
> > > + [67] = DHCP_OPT_STR, /* Bootfile Name */
> > > + [119] = DHCP_OPT_STR, /* Domain Search List */
> >
> > This is not really a string as this uses the message compression described
> > in RFC 1035,
> > 4.1.4. (See also 3. Example in rfc3397). I'm not sure we can encode this
> > manually on the
> > command line. And RFC 3396 defines how to encode search string for more
> > than 255
> > characters length
> >
> > > + [252] = DHCP_OPT_STR, /* WPAD URL */
> > > +};
> > > +
> > > +/**
> > > + * dhcp_opt_int_width - Integer width in bytes for INTEGER-typed options
> > > + */
> > > +static const uint8_t dhcp_opt_int_width[256] = {
> > > + [2] = 4, /* Time Offset */
> > > + [13] = 2, /* Boot File Size */
> > > + [19] = 1, /* IP Forwarding */
> > > + [23] = 1, /* Default IP TTL */
> > > + [26] = 2, /* Interface MTU */
> > > + [37] = 1, /* TCP Default TTL */
> > > + [38] = 4, /* TCP Keepalive Interval */
> > > + [51] = 4, /* IP Address Lease Time */
> > > + [53] = 1, /* DHCP Message Type */
> > > + [57] = 2, /* Max DHCP Message Size */
> > > + [58] = 4, /* Renewal (T1) Time */
> > > + [59] = 4, /* Rebinding (T2) Time */
> > > +};
> > > +
> > > +#define DHCP_OPT_PARSE_BUF 1024
> >
> > Do we need 1024 bytes, all options are bounded to 256 bytes.
> > > +
> > > +/**
> > > + * dhcp_opt_parse() - Parse a DHCP option value
> > > + * @code: DHCP option code
> > > + * @str: DHCP Value string from command line
> > > + * @buf: Output buffer
> > > + * @buf_len: Size of output buffer
> > > + *
> > > + * Return: number of bytes written to @buf, or -1 on error
> > > + */
> > > +int dhcp_opt_parse(uint8_t code, const char *str, uint8_t *buf, size_t
> > buf_len)
> > > +{
> > > + enum dhcp_opt_type type = dhcp_opt_types[code];
> > > + char tmp[DHCP_OPT_PARSE_BUF];
> > > + char *tok, *saveptr, *end;
> > > + struct in_addr addr;
> > > + unsigned long val;
> > > + unsigned int i;
> > > + uint8_t width;
> > > + size_t slen;
> > > + int len;
> > > +
> > > + switch (type) {
> > > + case DHCP_OPT_NONE:
> > > + die("Unsupported DHCP option: %u,"
> > > + " see passt(1) for supported codes", code);
> > > + case DHCP_OPT_IPV4:
> > > + if (inet_pton(AF_INET, str, &addr) != 1)
> > > + return -1;
> > > +
> > > + if (buf_len < sizeof(addr))
> > > + return -1;
> > > +
> > > + memcpy(buf, &addr, sizeof(addr));
> > > +
> > > + return sizeof(addr);
> > > + case DHCP_OPT_IPV4_LIST:
> > > + len = 0;
> > > +
> > > + if (snprintf_check(tmp, sizeof(tmp), "%s", str))
> > > + return -1;
> > > +
> > > + for (tok = strtok_r(tmp, ",", &saveptr); tok;
> > > + tok = strtok_r(NULL, ",", &saveptr)) {
> > > + if (inet_pton(AF_INET, tok, &addr) != 1)
> > > + return -1;
> > > +
> > > + if (len + (int)sizeof(addr) > (int)buf_len)
> > > + return -1;
> > > +
> > > + memcpy(buf + len, &addr, sizeof(addr));
> > > + len += sizeof(addr);
> > > + }
> > > + return len;
> > > + case DHCP_OPT_INTEGER:
> > > + width = dhcp_opt_int_width[code];
> > > + val = strtoul(str, &end, 0);
> > > +
> > > + if (*end || buf_len < width)
> > > + return -1;
> > > +
> > > + if (width < 4 && val >= (1UL << (width * 8)))
> > > + return -1;
> > > +
> > > + for (i = 0; i < width; i++)
> > > + buf[i] = (val >> ((width - 1 - i) * 8)) & 0xff;
> > > +
> > > + return width;
> > > + case DHCP_OPT_STR:
> > > + slen = strlen(str);
> > > +
> > > + if (!slen || slen >= buf_len)
> > > + return -1;
> > > +
> > > + strncpy((char *)buf, str, buf_len);
> > > +
> > > + return slen;
> > > + }
> > > +
> > > + return -1;
> > > +}
> > > +
> > > /**
> > > * struct opt - DHCP option
> > > * @sent: Convenience flag, set while filling replies
> > > diff --git a/dhcp.h b/dhcp.h
> > > index cd50c99..3da571c 100644
> > > --- a/dhcp.h
> > > +++ b/dhcp.h
> > > @@ -6,7 +6,24 @@
> > > #ifndef DHCP_H
> > > #define DHCP_H
> > >
> > > +/**
> > > + * enum dhcp_opt_type - DHCP option value types per RFC 2132
> > > + * @DHCP_OPT_NONE: Unsupported or unknown option
> > > + * @DHCP_OPT_STR: Variable-length string
> > > + * @DHCP_OPT_IPV4: Single IPv4 address
> > > + * @DHCP_OPT_IPV4_LIST:Multiple IPv4 addresses, comma-separated
> > > + * @DHCP_OPT_INTEGER: Unsigned integer (1, 2, or 4 bytes)
> > > + */
> > > +enum dhcp_opt_type {
> > > + DHCP_OPT_NONE,
> > > + DHCP_OPT_STR,
> > > + DHCP_OPT_IPV4,
> > > + DHCP_OPT_IPV4_LIST,
> > > + DHCP_OPT_INTEGER,
> > > +};
> > > +
> > > int dhcp(const struct ctx *c, struct iov_tail *data);
> > > void dhcp_init(void);
> > > +int dhcp_opt_parse(uint8_t code, const char *str, uint8_t *buf, size_t
> > buf_len);
> > >
> > > #endif /* DHCP_H */
> > > diff --git a/passt.h b/passt.h
> > > index 3a0816f..751fee3 100644
> > > --- a/passt.h
> > > +++ b/passt.h
> > > @@ -184,6 +184,8 @@ struct ip6_ctx {
> > > * @fqdn: Guest FQDN
> > > * @custom_opts: User-specified DHCP options from --dhcp-opt
> > > * @custom_opts.code: DHCP option code
> > > + * @custom_opts.len: Length of binary value in @val
> > > + * @custom_opts.val: Binary-encoded option value
> > > * @custom_opts.str: Original string value from command line
> > > * @custom_opts_count: Number of entries in @custom_opts
> > > * @ifi6: Template interface for IPv6, -1: none, 0: IPv6
> > disabled
> > > @@ -271,6 +273,8 @@ struct ctx {
> > >
> > > struct {
> > > uint8_t code;
> > > + uint8_t len;
> > > + uint8_t val[255];
> > > char str[256];
> >
> > Why do we need to keep str[] once the value is encoded into val[]?
> >
>
> To print the option value as entered by user.
Right, but I think Laurent's point is that it's unfortunate to keep
str[] around indefinitely for something that's used once at startup.
>
> anskuma@anskuma-thinkpadp1gen7:~/Documents/passt$ ./passt -f --dhcp-opt
> 60,HTTPClient --dhcp-opt 67,http://192.168.1.1:8080/alpine.iso --dhcp-opt
> 12,testhost --dhcp-opt 15,test.example.com --dhcp-opt 6,8.8.8.8,8.8.4.4
> --dhcp-opt 26,1400 --dhcp-opt 42,192.168.1.1 --dhcp-opt 51,360
> --dhcp-opt 6,1.1.1.1,9.9.9.9
> UNIX domain socket bound at /tmp/passt_1.socket
> No IPv6 nameserver available for NDP/DHCPv6
> Template interface: wlp9s0f0 (IPv4), wlp9s0f0 (IPv6)
> MAC:
> host: 9a:55:9a:55:9a:55
> NAT to host 127.0.0.1: 192.168.1.1
> DHCP:
> assign: 192.168.1.9
> mask: 255.255.255.0
> router: 192.168.1.1
>
>
>
>
>
>
>
> *option 60: HTTPClient option 67: http://192.168.1.1:8080/alpine.iso
> <http://192.168.1.1:8080/alpine.iso> option 12: testhost option 15:
> test.example.com <http://test.example.com> option 6: 1.1.1.1,9.9.9.9
> option 26: 1400 option 42: 192.168.1.1 option 51: 360*
>
>
> >
> > > } custom_opts[MAX_CUSTOM_DHCP_OPTS];
> > > int custom_opts_count;
> >
> > Thanks,
> > Laurent
> >
> >
--
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
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next prev parent reply other threads:[~2026-05-28 5:45 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-26 12:31 [PATCH v2 0/6] Add --dhcp-boot and --dhcp-opt options Anshu Kumari
2026-05-26 12:31 ` [PATCH v2 1/6] conf: Add --dhcp-opt command-line option Anshu Kumari
2026-05-26 13:19 ` Laurent Vivier
2026-05-27 2:51 ` David Gibson
2026-05-28 5:02 ` Anshu Kumari
2026-05-28 5:22 ` David Gibson
2026-05-27 7:23 ` Laurent Vivier
2026-05-26 12:31 ` [PATCH v2 2/6] conf: Add --dhcp-boot " Anshu Kumari
2026-05-26 13:25 ` Laurent Vivier
2026-05-27 2:52 ` David Gibson
2026-05-28 5:14 ` Anshu Kumari
2026-05-27 6:59 ` Laurent Vivier
2026-05-26 12:31 ` [PATCH v2 3/6] dhcp: Add option type table and value parser Anshu Kumari
2026-05-26 16:05 ` Laurent Vivier
2026-05-27 3:00 ` David Gibson
2026-05-28 5:39 ` Anshu Kumari
2026-05-28 5:45 ` David Gibson [this message]
2026-05-27 3:26 ` David Gibson
2026-05-26 12:31 ` [PATCH v2 4/6] dhcp: Refactor fill_one() to operate on a generic buffer Anshu Kumari
2026-05-26 16:13 ` Laurent Vivier
2026-05-27 3:46 ` David Gibson
2026-05-26 12:31 ` [PATCH v2 5/6] dhcp: Add option overload Anshu Kumari
2026-05-26 17:42 ` Laurent Vivier
2026-05-27 4:03 ` David Gibson
2026-05-28 7:18 ` Anshu Kumari
2026-05-26 12:31 ` [PATCH v2 6/6] doc: Add --dhcp-boot and --dhcp-opt to man page Anshu Kumari
2026-05-27 4:16 ` David Gibson
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