From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: passt.top; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: passt.top; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=FXseVZBA; dkim-atps=neutral Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by passt.top (Postfix) with ESMTPS id D551C5A0265 for ; Fri, 17 Jul 2026 19:58:39 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1784311118; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=UGBN3pEJrp8dw7u0pwVainTbj538X5/tsMwaqo+np7w=; b=FXseVZBAp31+kLYFYQYkngUn7NJImCntEQlqjXH+sGhiCaO6aYWYiLZT1um95lqm2Bc48V HeCAjSw0K32nm5Ryc6vdwev6SVPE5Ly3XNv6gyNj4Wa+RZYeJ6bxo9WJHyupGyHe7akAod TC0Jz/2ZsSZ/FVc4PH5uIO1WcmkhoZU= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-659-whvK-5JLPbiTkJui4-fF5g-1; Fri, 17 Jul 2026 13:57:26 -0400 X-MC-Unique: whvK-5JLPbiTkJui4-fF5g-1 X-Mimecast-MFC-AGG-ID: whvK-5JLPbiTkJui4-fF5g_1784311046 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 6B53718009EA; Fri, 17 Jul 2026 17:57:25 +0000 (UTC) Received: from anskuma-thinkpadp1gen7.bengluru.csb (unknown [10.74.80.5]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 8475D180025F; Fri, 17 Jul 2026 17:57:22 +0000 (UTC) From: Anshu Kumari To: anskuma@redhat.com, sbrivio@redhat.com, passt-dev@passt.top Subject: [PATCH v5 6/7] dhcp: Add RFC 3396 option splitting for concatenation-requiring options Date: Fri, 17 Jul 2026 23:26:43 +0530 Message-ID: <20260717175648.879152-7-anskuma@redhat.com> In-Reply-To: <20260717175648.879152-1-anskuma@redhat.com> References: <20260717175648.879152-1-anskuma@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: UJQUK77EMs6E1xMnfyplw9FvTCmvKGEscWx9mULfgoc_1784311046 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true Message-ID-Hash: TBUBYK4HVJOXCYUFK3B3YBFI5D4K66QB X-Message-ID-Hash: TBUBYK4HVJOXCYUFK3B3YBFI5D4K66QB X-MailFrom: anskuma@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: lvivier@redhat.com, david@gibson.dropbear.id.au, jmaloy@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: Implement option splitting per RFC 3396 for options that may exceed 255 bytes. A new DHCP_OPT_STR_CONCAT type marks concatenation- requiring options (currently option 81, Client FQDN per RFC 4702). The opts[].s buffer is resized from 255 to 496 bytes to hold the maximum data that can be split across the options field, file field, and sname field. When a concatenation-requiring option does not fit as a single option in any field, fill() splits it across fields in RFC 3396 order: options field first, then file, then sname. Link: https://bugs.passt.top/show_bug.cgi?id=192 Signed-off-by: Anshu Kumari --- v5: - New patch: implement option splitting per RFC 3396 for options exceeding 255 bytes - Add DHCP_OPT_STR_CONCAT type, is_concat_opt(), fill_split() helpers - Resize opts[].s from 255 to OPT_CONCAT_MAX (496) bytes - Add /* fallthrough */ between DHCP_OPT_STR and DHCP_OPT_STR_CONCAT case --- dhcp.c | 109 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 106 insertions(+), 3 deletions(-) diff --git a/dhcp.c b/dhcp.c index cc910ee..6bebb5f 100644 --- a/dhcp.c +++ b/dhcp.c @@ -34,6 +34,11 @@ #include "log.h" #include "dhcp.h" +/* RFC 3396: maximum option data that can be split across options field, + * file field, and sname field (minus code+length overhead per portion). + */ +#define OPT_CONCAT_MAX 496 + /** * enum opt_state - DHCP option state * @OPT_UNSET: Option not configured @@ -58,7 +63,7 @@ enum opt_state { struct opt { int sent; int slen; - uint8_t s[255]; + uint8_t s[OPT_CONCAT_MAX]; int clen; uint8_t c[255]; enum opt_state state; @@ -159,6 +164,7 @@ struct msg { * @DHCP_OPT_UINT16: Unsigned 16-bit integer * @DHCP_OPT_UINT32: Unsigned 32-bit integer * @DHCP_OPT_INT32: Signed 32-bit integer + * @DHCP_OPT_STR_CONCAT:Concatenation-requiring string (RFC 3396) */ enum dhcp_opt_type { DHCP_OPT_NONE, @@ -169,6 +175,7 @@ enum dhcp_opt_type { DHCP_OPT_UINT16, DHCP_OPT_UINT32, DHCP_OPT_INT32, + DHCP_OPT_STR_CONCAT, }; /** @@ -319,6 +326,10 @@ static int dhcp_opt_parse(uint8_t code, const char *str, return width; case DHCP_OPT_STR: + if (strlen(str) > 255) + return -1; + /* fallthrough */ + case DHCP_OPT_STR_CONCAT: slen = strlen(str); if (slen >= buf_len) @@ -465,6 +476,53 @@ enum dhcp_overload { DHCP_OVERLOAD_SNAME, }; +/** + * is_concat_opt() - Check if option requires RFC 3396 concatenation support + * @o: Option number + * + * Return: true if option is a concatenation-requiring type + */ +static bool is_concat_opt(int o) +{ + if ((size_t)o >= ARRAY_SIZE(dhcp_opt_types)) + return false; + return dhcp_opt_types[o] == DHCP_OPT_STR_CONCAT; +} + +/** + * fill_split() - Write a split portion of an option into a buffer + * @buf: Buffer to write into + * @size: Usable size of @buf + * @o: Option number (code) + * @offset: Current offset within @buf, updated on write + * @data: Pointer to remaining option data to write + * @remaining: Bytes of option data still to write + * + * Return: number of data bytes written (excluding code+length header) + */ +static size_t fill_split(uint8_t *buf, size_t size, int o, int *offset, + const uint8_t *data, size_t remaining) +{ + size_t avail, chunk; + + if (*offset + 2 >= (int)size) + return 0; + + avail = size - *offset - 2; + chunk = remaining < avail ? remaining : avail; + if (!chunk) + return 0; + + buf[*offset] = o; + buf[*offset + 1] = chunk; + *offset += 2; + + memcpy(buf + *offset, data, chunk); + *offset += chunk; + + return chunk; +} + /** * fill() - Fill options in message, with overload into file/sname if needed * @m: Message to fill @@ -513,14 +571,59 @@ static int fill(struct msg *m, enum dhcp_overload *overload, bool has_bootfile) for (o = 0; (size_t)o < ARRAY_SIZE(opts); o++) { if (opts[o].state == OPT_UNSET || opts[o].sent) continue; - if (!has_bootfile && fill_one(m->file, sizeof(m->file) - 1, o, - &file_off)) + &file_off)) + if (!is_concat_opt(o)) debug("DHCP: skipping option %i" " (overload full)", o); } + /* RFC 3396: split concatenation-requiring options that didn't fit + * as a single option. Split order: options, file, sname. + */ + for (o = 0; (size_t)o < ARRAY_SIZE(opts); o++) { + size_t file_cap, sname_cap, total, written; + + if (opts[o].state == OPT_UNSET || opts[o].sent || + !is_concat_opt(o)) + continue; + + sname_cap = sizeof(m->sname) - 1 > (size_t)sname_off ? + sizeof(m->sname) - 1 - sname_off : 0; + + if (has_bootfile || sizeof(m->file) - 1 <= (size_t)file_off) + file_cap = 0; + else + file_cap = sizeof(m->file) - 1 - file_off; + + total = (size > (size_t)offset ? size - offset : 0) + + file_cap + sname_cap; + + if (total < (size_t)opts[o].slen) { + debug("DHCP: skipping option %i (no space to split)", + o); + continue; + } + + written = 0; + written += fill_split(m->o, size, o, &offset, + opts[o].s, opts[o].slen); + if (written < (size_t)opts[o].slen && !has_bootfile) + written += fill_split(m->file, + sizeof(m->file) - 1, o, + &file_off, + opts[o].s + written, + opts[o].slen - written); + if (written < (size_t)opts[o].slen) + fill_split(m->sname, + sizeof(m->sname) - 1, o, + &sname_off, + opts[o].s + written, + opts[o].slen - written); + opts[o].sent = 1; + } + if (sname_off) { m->sname[sname_off] = 255; *overload |= DHCP_OVERLOAD_SNAME; -- 2.54.0