Re: [PATCH v5 16/29] dhcpv6: Use iov_tail in dhcpv6_opt()

On Thu, 17 Apr 2025 18:51:23 +0200 Laurent Vivier wrote:

Signed-off-by: Laurent Vivier --- dhcpv6.c | 179 ++++++++++++++++++++++++++++++++----------------------- iov.c | 1 - 2 files changed, 103 insertions(+), 77 deletions(-)

diff --git a/dhcpv6.c b/dhcpv6.c index a52af1b7a0fe..365b609addda 100644 --- a/dhcpv6.c +++ b/dhcpv6.c @@ -278,112 +278,122 @@ static struct resp_not_on_link_t {

/** * dhcpv6_opt() - Get option from DHCPv6 message - * @p: Packet pool, single packet with UDP header - * @offset: Offset to look at, 0: end of header, set to option start + * @data: Data to look at (input/output)

This isn't really clear to me. I'd rather say it's data where we look for options, and that it's set to the option on return, maybe: @data: Buffer with options, set to matching option on return ?

* @type: Option type to look up, network order * - * Return: pointer to option header, or NULL on malformed or missing option + * Return: true if found and @data points to the option header, + * or false on malformed or missing option and @data is + * unmodified. */ -static struct opt_hdr *dhcpv6_opt(const struct pool *p, size_t *offset, - uint16_t type) +static bool dhcpv6_opt(struct iov_tail *data, uint16_t type) { - struct opt_hdr *o; - size_t left; + struct iov_tail head = *data; + const struct opt_hdr *o; + struct opt_hdr oc;

- ASSERT(*offset >= UDP_MSG_HDR_SIZE); - - while ((o = packet_get_try(p, 0, *offset, sizeof(*o), &left))) { + while ((o = IOV_PEEK_HEADER(data, oc))) { unsigned int opt_len = ntohs(o->l) + sizeof(*o);

- if (ntohs(o->l) > left) - return NULL; + if (opt_len > iov_tail_size(data)) + break;

if (o->t == type) - return o; + return true;

- *offset += opt_len; + iov_tail_drop(data, opt_len); }

- return NULL; + *data = head; + return false; }

/** * dhcpv6_ia_notonlink() - Check if any IA contains non-appropriate addresses - * @p: Packet pool, single packet starting from UDP header + * @data: Data to look at, packet starting from UDP header (input/output) * @la: Address we want to lease to the client * - * Return: pointer to non-appropriate IA_NA or IA_TA, if any, NULL otherwise + * Return: true and @data points to non-appropriate IA_NA or IA_TA, if any, + * false otherwise and @data is unmodified */ -static struct opt_hdr *dhcpv6_ia_notonlink(const struct pool *p, - struct in6_addr *la) +static bool dhcpv6_ia_notonlink(struct iov_tail *data, + struct in6_addr *la) { int ia_types[2] = { OPT_IA_NA, OPT_IA_TA }, *ia_type; const struct opt_ia_addr *opt_addr; + struct iov_tail current, ia_base; + struct opt_ia_addr opt_addrc; char buf[INET6_ADDRSTRLEN]; + const struct opt_ia_na *ia; struct in6_addr req_addr; const struct opt_hdr *h; - struct opt_hdr *ia; - size_t offset; + struct opt_ia_na iac; + struct opt_hdr hc;

foreach(ia_type, ia_types) { - offset = UDP_MSG_HDR_SIZE; - while ((ia = dhcpv6_opt(p, &offset, *ia_type))) { - if (ntohs(ia->l) < OPT_VSIZE(ia_na)) - return NULL; - - offset += sizeof(struct opt_ia_na); - - while ((h = dhcpv6_opt(p, &offset, OPT_IAAADR))) { - if (ntohs(h->l) != OPT_VSIZE(ia_addr)) - return NULL; - - opt_addr = (const struct opt_ia_addr *)h; + current = *data; + while (dhcpv6_opt(¤t, *ia_type)) { + ia_base = current; + ia = IOV_REMOVE_HEADER(¤t, iac); + if (!ia || ntohs(ia->hdr.l) < OPT_VSIZE(ia_na)) + goto notfound; + + while (dhcpv6_opt(¤t, OPT_IAAADR)) { + h = IOV_PEEK_HEADER(¤t, hc); + if (!h || ntohs(h->l) != OPT_VSIZE(ia_addr)) + goto notfound; + + opt_addr = IOV_REMOVE_HEADER(¤t, + opt_addrc); req_addr = opt_addr->addr; if (!IN6_ARE_ADDR_EQUAL(la, &req_addr)) - goto err; - - offset += sizeof(struct opt_ia_addr); + goto notonlink; } } }

- return NULL; +notfound: + return false;

-err: +notonlink: info("DHCPv6: requested address %s not on link", inet_ntop(AF_INET6, &req_addr, buf, sizeof(buf))); - return ia; + *data = ia_base; + return true; }

/** * dhcpv6_send_ia_notonlink() - Send NotOnLink status - * @c: Execution context - * @ia: Pointer to non-appropriate IA_NA or IA_TA - * @client_id: Client ID message option - * xid: Transaction ID for message exchange + * @c: Execution context + * @ia_base: Non-appropriate IA_NA or IA_TA base + * @client_id_base: Client ID message option base + * @len: Client ID length + * @xid: Transaction ID for message exchange */ -static void dhcpv6_send_ia_notonlink(struct ctx *c, struct opt_hdr *ia, - const struct opt_hdr *client_id, - uint32_t xid) +static void dhcpv6_send_ia_notonlink(struct ctx *c, + const struct iov_tail *ia_base, + const struct iov_tail *client_id_base, + int len, uint32_t xid) { const struct in6_addr *src = &c->ip6.our_tap_ll; + struct opt_hdr *ia = (struct opt_hdr *)resp_not_on_link.var; size_t n;

info("DHCPv6: received CONFIRM with inappropriate IA," " sending NotOnLink status in REPLY");

- ia->l = htons(OPT_VSIZE(ia_na) + sizeof(sc_not_on_link)); - n = sizeof(struct opt_ia_na); - memcpy(resp_not_on_link.var, ia, n); + iov_to_buf(&ia_base->iov[0], ia_base->cnt, ia_base->off, + resp_not_on_link.var, n); + ia->l = htons(OPT_VSIZE(ia_na) + sizeof(sc_not_on_link)); memcpy(resp_not_on_link.var + n, &sc_not_on_link, sizeof(sc_not_on_link));

n += sizeof(sc_not_on_link); - memcpy(resp_not_on_link.var + n, client_id, - sizeof(struct opt_hdr) + ntohs(client_id->l)); + iov_to_buf(&client_id_base->iov[0], client_id_base->cnt, + client_id_base->off, resp_not_on_link.var + n, + sizeof(struct opt_hdr) + len);

- n += sizeof(struct opt_hdr) + ntohs(client_id->l); + n += sizeof(struct opt_hdr) + len;

n = offsetof(struct resp_not_on_link_t, var) + n;

@@ -472,17 +482,19 @@ search:

/** * dhcpv6_client_fqdn_fill() - Fill in client FQDN option + * @data: Data to look at * @c: Execution context * @buf: Response message buffer where options will be appended * @offset: Offset in message buffer for new options * * Return: updated length of response message buffer. */ -static size_t dhcpv6_client_fqdn_fill(const struct pool *p, const struct ctx *c, +static size_t dhcpv6_client_fqdn_fill(const struct iov_tail *data, + const struct ctx *c, char *buf, int offset)

{ - struct opt_client_fqdn const *req_opt; + struct iov_tail current = *data; struct opt_client_fqdn *o; size_t opt_len;

@@ -501,13 +513,16 @@ static size_t dhcpv6_client_fqdn_fill(const struct pool *p, const struct ctx *c,

o = (struct opt_client_fqdn *)(buf + offset); encode_domain_name(o->domain_name, c->fqdn); - req_opt = (struct opt_client_fqdn *)dhcpv6_opt(p, - &(size_t){ UDP_MSG_HDR_SIZE }, - OPT_CLIENT_FQDN); - if (req_opt && req_opt->flags & 0x01 /* S flag */) - o->flags = 0x02 /* O flag */; - else - o->flags = 0x00; + if (dhcpv6_opt(¤t, OPT_CLIENT_FQDN)) { + struct opt_client_fqdn const *req_opt; + struct opt_client_fqdn req_optc; + + req_opt = IOV_PEEK_HEADER(¤t, req_optc); + if (req_opt && req_opt->flags & 0x01 /* S flag */) + o->flags = 0x02 /* O flag */; + else + o->flags = 0x00; + }

Earlier, if we didn't find the option, we would set o->flags to 0x00. Now we do nothing. -- Stefano