From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: passt.top; dmarc=none (p=none dis=none) header.from=gibson.dropbear.id.au Authentication-Results: passt.top; dkim=pass (2048-bit key; secure) header.d=gibson.dropbear.id.au header.i=@gibson.dropbear.id.au header.a=rsa-sha256 header.s=202602 header.b=HNX/0noH; dkim-atps=neutral Received: from mail.ozlabs.org (gandalf.ozlabs.org [150.107.74.76]) by passt.top (Postfix) with ESMTPS id 5A2975A026D for ; Wed, 27 May 2026 05:26:27 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gibson.dropbear.id.au; s=202602; t=1779852384; bh=8EbjmcdYtuxkrY9/HfNMNVZxErw0UGFxHbYVgl1+YMg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=HNX/0noHQ+rFZEQ8NdyWmFpjZvstbcaF72XW4mETsx8qvKmh3H9/lU0Xr3VVhwyIQ Sgw4LeN12kpXEuVgfFUsmdvlFZhySTb0r075QTe012hLJO7ZEM7kctofpPWahI71ml pSq6cwZpTXwPgZhr1G0MY0ar3d/R4FoPfDhE9N4+YMncDcww1Bv2yW/HUFaECC9bV2 STckB+KPLNeUdmyJk+z2DugPffE3sVjtoM4vq6izyxl/ZwYoCtF2bOXnJibDAyGHhc o8dZg0igYWBuc+G4+/v1hwGr/SS40mt/a5uQp2MItx0B+trl1f2b2jVyDkspQT2Asf UNV3poPy4vESQ== Received: by gandalf.ozlabs.org (Postfix, from userid 1007) id 4gQFQS0QSRz4wCH; Wed, 27 May 2026 13:26:24 +1000 (AEST) Date: Wed, 27 May 2026 13:26:03 +1000 From: David Gibson To: Anshu Kumari Subject: Re: [PATCH v2 3/6] dhcp: Add option type table and value parser Message-ID: References: <20260526123115.1226166-1-anskuma@redhat.com> <20260526123115.1226166-4-anskuma@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="Il9yAQ5P45UKDEEx" Content-Disposition: inline In-Reply-To: <20260526123115.1226166-4-anskuma@redhat.com> Message-ID-Hash: OBXZHM2TZQOM4C5PLRPJGYM6KN26S6GY X-Message-ID-Hash: OBXZHM2TZQOM4C5PLRPJGYM6KN26S6GY X-MailFrom: dgibson@gandalf.ozlabs.org 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, sbrivio@redhat.com, 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: --Il9yAQ5P45UKDEEx Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, May 26, 2026 at 06:01:10PM +0530, 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. >=20 > Wire dhcp_opt_parse() into the --dhcp-opt handler so that values are > validated and encoded at configuration time. >=20 > Link: https://bugs.passt.top/show_bug.cgi?id=3D192 > Signed-off-by: Anshu Kumari Laurent's comments seconded, a few other ones here. > --- > v2: > - Replaced struct lookup table + dhcp_opt_type_lookup() function with f= lat dhcp_opt_types[256] array indexed by code. > - Consolidated DHCP_OPT_UINT8/UINT16/UINT32 into single DHCP_OPT_INTEGE= R 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= =2E8.8.8). > - Defined DHCP_OPT_PARSE_BUF constant for bare 1024. > - Added len and val[255] fields to struct here (moved from patch=A01). > - 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(+) >=20 > 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; > =09 > =20 > if (c->mode =3D=3D 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); > =20 > + ret =3D 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 =3D 67; > + c->custom_opts[c->custom_opts_count].len =3D 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); > =20 > + len =3D dhcp_opt_parse(optcode, comma + 1, > + c->custom_opts[c->custom_opts_count].val, > + sizeof(c->custom_opts[0].val)); > + if (len < 0) > + die("Invalid value for DHCP option %lu: %s", > + optcode, comma + 1); > + > c->custom_opts[c->custom_opts_count].code =3D optcode; > + c->custom_opts[c->custom_opts_count].len =3D 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" > =20 > +/** > + * dhcp_opt_types - Maps option code to RFC 2132 value type, indexed by = code > + */ > +static const enum dhcp_opt_type dhcp_opt_types[256] =3D { > + [1] =3D DHCP_OPT_IPV4, /* Subnet Mask */ > + [2] =3D DHCP_OPT_INTEGER, /* Time Offset */ > + [3] =3D DHCP_OPT_IPV4_LIST, /* Router */ > + [4] =3D DHCP_OPT_IPV4_LIST, /* Time Server */ > + [5] =3D DHCP_OPT_IPV4_LIST, /* Name Server */ > + [6] =3D DHCP_OPT_IPV4_LIST, /* Domain Name Server */ > + [7] =3D DHCP_OPT_IPV4_LIST, /* Log Server */ > + [8] =3D DHCP_OPT_IPV4_LIST, /* Cookie Server */ > + [9] =3D DHCP_OPT_IPV4_LIST, /* LPR Server */ > + [10] =3D DHCP_OPT_IPV4_LIST, /* Impress Server */ > + [11] =3D DHCP_OPT_IPV4_LIST, /* Resource Location Server */ > + [12] =3D DHCP_OPT_STR, /* Host Name */ > + [13] =3D DHCP_OPT_INTEGER, /* Boot File Size */ > + [15] =3D DHCP_OPT_STR, /* Domain Name */ > + [16] =3D DHCP_OPT_IPV4, /* Swap Server */ > + [17] =3D DHCP_OPT_STR, /* Root Path */ > + [19] =3D DHCP_OPT_INTEGER, /* IP Forwarding */ > + [23] =3D DHCP_OPT_INTEGER, /* Default IP TTL */ > + [26] =3D DHCP_OPT_INTEGER, /* Interface MTU */ > + [28] =3D DHCP_OPT_IPV4, /* Broadcast Address */ > + [33] =3D DHCP_OPT_IPV4_LIST, /* Static Routes */ > + [37] =3D DHCP_OPT_INTEGER, /* TCP Default TTL */ > + [38] =3D DHCP_OPT_INTEGER, /* TCP Keepalive Interval */ > + [40] =3D DHCP_OPT_STR, /* NIS Domain Name */ > + [41] =3D DHCP_OPT_IPV4_LIST, /* NIS Servers */ > + [42] =3D DHCP_OPT_IPV4_LIST, /* NTP Servers */ > + [44] =3D DHCP_OPT_IPV4_LIST, /* NetBIOS Name Server */ > + [50] =3D DHCP_OPT_IPV4, /* Requested IP Address */ > + [51] =3D DHCP_OPT_INTEGER, /* IP Address Lease Time */ > + [53] =3D DHCP_OPT_INTEGER, /* DHCP Message Type */ > + [54] =3D DHCP_OPT_IPV4, /* Server Identifier */ > + [55] =3D DHCP_OPT_STR, /* Parameter Request List */ > + [57] =3D DHCP_OPT_INTEGER, /* Max DHCP Message Size */ > + [58] =3D DHCP_OPT_INTEGER, /* Renewal (T1) Time */ > + [59] =3D DHCP_OPT_INTEGER, /* Rebinding (T2) Time */ > + [60] =3D DHCP_OPT_STR, /* Vendor Class Identifier */ > + [61] =3D DHCP_OPT_STR, /* Client Identifier */ > + [66] =3D DHCP_OPT_STR, /* TFTP Server Name */ > + [67] =3D DHCP_OPT_STR, /* Bootfile Name */ > + [119] =3D DHCP_OPT_STR, /* Domain Search List */ > + [252] =3D 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] =3D { I know I suggested this approach, but now seeing a whole array[256] it seems unpleasantly bulky. I'd suggest instead encoding the width into some bits of the DHCP_OPT_* constants. > + [2] =3D 4, /* Time Offset */ > + [13] =3D 2, /* Boot File Size */ > + [19] =3D 1, /* IP Forwarding */ > + [23] =3D 1, /* Default IP TTL */ > + [26] =3D 2, /* Interface MTU */ > + [37] =3D 1, /* TCP Default TTL */ > + [38] =3D 4, /* TCP Keepalive Interval */ > + [51] =3D 4, /* IP Address Lease Time */ > + [53] =3D 1, /* DHCP Message Type */ > + [57] =3D 2, /* Max DHCP Message Size */ > + [58] =3D 4, /* Renewal (T1) Time */ > + [59] =3D 4, /* Rebinding (T2) Time */ > +}; > + > +#define DHCP_OPT_PARSE_BUF 1024 > + > +/** > + * 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 b= uf_len) > +{ > + enum dhcp_opt_type type =3D 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) !=3D 1) > + return -1; > + > + if (buf_len < sizeof(addr)) > + return -1; > + > + memcpy(buf, &addr, sizeof(addr)); > + > + return sizeof(addr); > + case DHCP_OPT_IPV4_LIST: I think it should be possible to share more logic between the single IPv4 and IPv4 list options (parse them both as a list, but error if there's >1 in the single case). > + len =3D 0; > + > + if (snprintf_check(tmp, sizeof(tmp), "%s", str)) > + return -1; > + > + for (tok =3D strtok_r(tmp, ",", &saveptr); tok; > + tok =3D strtok_r(NULL, ",", &saveptr)) { > + if (inet_pton(AF_INET, tok, &addr) !=3D 1) > + return -1; > + > + if (len + (int)sizeof(addr) > (int)buf_len) > + return -1; > + > + memcpy(buf + len, &addr, sizeof(addr)); > + len +=3D sizeof(addr); > + } > + return len; > + case DHCP_OPT_INTEGER: > + width =3D dhcp_opt_int_width[code]; > + val =3D strtoul(str, &end, 0); Most strtoul() errors can be discerned by checking end, but not all. You also need to explicitly set errno to 0 beforehand and check it again afterwards (clunky, but that's the interface we have). > + > + if (*end || buf_len < width) > + return -1; > + > + if (width < 4 && val >=3D (1UL << (width * 8))) strtoul() will parse 64-bit values on most current platforms, so you need this range enforcement for width=3D=3D4 as well. > + return -1; > + > + for (i =3D 0; i < width; i++) > + buf[i] =3D (val >> ((width - 1 - i) * 8)) & 0xff; Might be easier to follow as: for (...) { buf[i] =3D val & 0xff; val >>=3D 8; } > + > + return width; > + case DHCP_OPT_STR: > + slen =3D strlen(str); > + > + if (!slen || slen >=3D buf_len) > + return -1; > + > + strncpy((char *)buf, str, buf_len); You've already know the length so you can make this a memcpy(). > + > + 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 > =20 > +/** > + * 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, > +}; This can move to dhcp.c, since it's not used in any other files. > + > 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 b= uf_len); > =20 > #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 { > =20 > struct { > uint8_t code; > + uint8_t len; > + uint8_t val[255]; > char str[256]; > } custom_opts[MAX_CUSTOM_DHCP_OPTS]; > int custom_opts_count; > --=20 > 2.54.0 >=20 --=20 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 --Il9yAQ5P45UKDEEx Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iQIzBAEBCgAdFiEEO+dNsU4E3yXUXRK2zQJF27ox2GcFAmoWZEoACgkQzQJF27ox 2GcNqw/9EfF4FxNuMsUnI7WQtHVeofbJHue4fUTlx2dH322vlM5LTTUBEJ21xfrc qp7i8EMkj+8mROpTP6HzkCGQHryT3FpMk3QsBWdE8ROlge53CkMJGJlBq3Wv1qf7 9ss6HbadnGrpKznGsZnaxjBm5TAbPkCtcJ0ugp2v+jS+YPFkOKJZD5nhuN8n4Bhl ElaLuXrGdBfL5u8jR9fs2U8kVsEdViX3aLLIP3YE3u7opxl7nEjksv/nBp6Fiqcg kOIXZ1SNCAp0zdsmwvnA8zYLOXt6DbqXSr23iHs8e7PR+F4a23UNYKnG/KVx+rr+ 6qMzhoTNXT7vXmF+pzOzSoiLNM+vdskzfLHbOAtVzpiyxHv6ZC2ykLJQD7diOwQc owzddXfn/f7NEPvXz123vT12+UxrQy1EbDxeHpyJrQXBDNAXk+m73vP2WLKa/rPc J6eqytIB/eSuLhWNbhd9hXRajxJVVAnG7hZKEd+MCdMidxLkx98ubPMReMCw79D/ OjhSi7OU2CGYCJn8bVjXkpeTtpCWRDeUuAJkevcH/dLMqtwTqvwLkq+ISqYfv05G otqA4uMB8BRSXO2vAPrkk3Hc1wUSGdbwU5rpldTc1jOy/VpUG1YXD+zcxXQsGN/1 +iOAGfP30ez0qAgUDcvqRd1eDk/4PolZiDVNqwsc9Qup8c41U4c= =9tJ+ -----END PGP SIGNATURE----- --Il9yAQ5P45UKDEEx--