Overloading slen = -1 to mean "not set" conflates the option
length with its lifecycle state, and can't express additional
states such as "set by the user via command-line" which will
be needed for --dhcp-opt support.
Introduce enum opt_state with OPT_UNSET (option not
configured) and OPT_DEFAULT (derived from host
configuration). Replace all slen = -1 / slen != -1 checks
with state comparisons, and set state = OPT_DEFAULT for
options initialised in dhcp_init() and at reply time in
dhcp().
Link: https://bugs.passt.top/show_bug.cgi?id=192
Signed-off-by: Anshu Kumari
---
v6:
- Rewrote commit message to explain why slen = -1 overloading
is problematic and how it motivates the enum.
- Dropped explicit OPT_UNSET initialization loop inside dhcp_init().
- Realigned opts[51] initializer for consistency.
v5:
- New patch: introduce enum opt_state { OPT_UNSET, OPT_DEFAULT } to replace slen = -1 for tracking option state
- Replace all slen = -1 / slen != -1 checks with state = OPT_UNSET / state != OPT_UNSET
- Set OPT_DEFAULT for options initialised in dhcp_init() and at reply time
---
dhcp.c | 58 ++++++++++++++++++++++++++++++++++++++--------------------
1 file changed, 38 insertions(+), 20 deletions(-)
diff --git a/dhcp.c b/dhcp.c
index bb72b72..321968a 100644
--- a/dhcp.c
+++ b/dhcp.c
@@ -33,13 +33,24 @@
#include "log.h"
#include "dhcp.h"
+/**
+ * enum opt_state - DHCP option state
+ * @OPT_UNSET: Option not configured
+ * @OPT_DEFAULT: Option derived from host configuration
+ */
+enum opt_state {
+ OPT_UNSET = 0,
+ OPT_DEFAULT,
+};
+
/**
* struct opt - DHCP option
* @sent: Convenience flag, set while filling replies
- * @slen: Length of option defined for server, -1 if not going to be sent
+ * @slen: Length of option defined for server
* @s: Option payload from server
* @clen: Length of option received from client, -1 if not received
* @c: Option payload from client
+ * @state: Option state (unset or default)
*/
struct opt {
int sent;
@@ -47,6 +58,7 @@ struct opt {
uint8_t s[255];
int clen;
uint8_t c[255];
+ enum opt_state state;
};
static struct opt opts[256];
@@ -73,19 +85,17 @@ static struct opt opts[256];
*/
void dhcp_init(void)
{
- int i;
-
- for (i = 0; i < ARRAY_SIZE(opts); i++)
- opts[i].slen = -1;
-
- opts[1] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, }; /* Mask */
- opts[3] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, }; /* Router */
- opts[51] = (struct opt) { 0, 4, { 0xff,
- 0xff,
- 0xff,
- 0xff }, 0, { 0 }, }; /* Lease time */
- opts[53] = (struct opt) { 0, 1, { 0 }, 0, { 0 }, }; /* Type */
- opts[54] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, }; /* Server ID */
+ /* Mask */
+ opts[1] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, OPT_DEFAULT, };
+ /* Router */
+ opts[3] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, OPT_DEFAULT, };
+ /* Lease time */
+ opts[51] = (struct opt) { 0, 4, { 0xff, 0xff, 0xff, 0xff },
+ 0, { 0 }, OPT_DEFAULT };
+ /* Type */
+ opts[53] = (struct opt) { 0, 1, { 0 }, 0, { 0 }, OPT_DEFAULT, };
+ /* Server ID */
+ opts[54] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, OPT_DEFAULT, };
}
/**
@@ -183,13 +193,13 @@ static int fill(struct msg *m)
for (i = 0; i < opts[55].clen; i++) {
o = opts[55].c[i];
- if (opts[o].slen != -1)
+ if (opts[o].state != OPT_UNSET)
if (fill_one(m->o, OPT_MAX, o, &offset))
debug("DHCP: skipping option %i", o);
}
for (o = 0; o < 255; o++) {
- if (opts[o].slen != -1 && !opts[o].sent)
+ if (opts[o].state != OPT_UNSET && !opts[o].sent)
if (fill_one(m->o, OPT_MAX, o, &offset))
debug("DHCP: skipping option %i", o);
}
@@ -243,6 +253,7 @@ static void opt_set_dns_search(const struct ctx *c, size_t max_len)
int i;
opts[119].slen = 0;
+ opts[119].state = OPT_DEFAULT;
for (i = 0; i < 255; i++)
max_len -= opts[i].slen;
@@ -291,7 +302,7 @@ static void opt_set_dns_search(const struct ctx *c, size_t max_len)
}
if (!opts[119].slen)
- opts[119].slen = -1;
+ opts[119].state = OPT_UNSET;
}
/**
@@ -389,7 +400,7 @@ int dhcp(const struct ctx *c, struct iov_tail *data)
iov_drop_header(data, *olen);
}
- opts[80].slen = -1;
+ opts[80].state = OPT_UNSET;
if (opts[53].clen > 0 && opts[53].c[0] == DHCPDISCOVER) {
if (opts[80].clen == -1) {
info("DHCP: offer to discover");
@@ -398,6 +409,7 @@ int dhcp(const struct ctx *c, struct iov_tail *data)
info("DHCP: ack to discover (Rapid Commit)");
opts[53].s[0] = DHCPACK;
opts[80].slen = 0;
+ opts[80].state = OPT_DEFAULT;
}
} else if (opts[53].clen <= 0 || opts[53].c[0] == DHCPREQUEST) {
info("%s: ack to request", /* DHCP needs a valid message type */
@@ -421,6 +433,7 @@ int dhcp(const struct ctx *c, struct iov_tail *data)
!= (c->ip4.guest_gw.s_addr & mask.s_addr)) {
/* a.b.c.d/32:0.0.0.0, 0:a.b.c.d */
opts[121].slen = 14;
+ opts[121].state = OPT_DEFAULT;
opts[121].s[0] = 32;
memcpy(opts[121].s + 1,
&c->ip4.guest_gw, sizeof(c->ip4.guest_gw));
@@ -430,6 +443,7 @@ int dhcp(const struct ctx *c, struct iov_tail *data)
if (c->mtu) {
opts[26].slen = 2;
+ opts[26].state = OPT_DEFAULT;
opts[26].s[0] = c->mtu / 256;
opts[26].s[1] = c->mtu % 256;
}
@@ -441,12 +455,15 @@ int dhcp(const struct ctx *c, struct iov_tail *data)
((struct in_addr *)opts[6].s)[i] = c->ip4.dns[i];
opts[6].slen += sizeof(uint32_t);
}
- if (!opts[6].slen)
- opts[6].slen = -1;
+ if (opts[6].slen)
+ opts[6].state = OPT_DEFAULT;
+ else
+ opts[6].state = OPT_UNSET;
opt_len = strlen(c->hostname);
if (opt_len > 0) {
opts[12].slen = opt_len;
+ opts[12].state = OPT_DEFAULT;
memcpy(opts[12].s, &c->hostname, opt_len);
}
@@ -463,6 +480,7 @@ int dhcp(const struct ctx *c, struct iov_tail *data)
encode_domain_name((char *)opts[81].s + 3, c->fqdn);
opts[81].slen = opt_len;
+ opts[81].state = OPT_DEFAULT;
} else {
debug("DHCP: client FQDN option doesn't fit, skipping");
}
--
2.55.0