Re: [PATCH v5 2/7] dhcp: Add option state management with enum opt_state

On Fri, 17 Jul 2026 23:26:39 +0530 Anshu Kumari wrote:

Introduce enum opt_state to track each DHCP option instead of overloading slen = -1 for "not set".

OPT_UNSET means the option is not configured. OPT_DEFAULT means the option was set from host configuration.

This replaces all slen = -1 / slen != -1 checks with state = OPT_UNSET / state != OPT_UNSET, and sets 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 --- 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 | 57 ++++++++++++++++++++++++++++++++++++++++----------------- 1 file changed, 40 insertions(+), 17 deletions(-)

diff --git a/dhcp.c b/dhcp.c index bb72b72..e5d89fc 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 set from host config

Nit: "config" isn't an actual word, it's a common abbreviation, but here we don't need it and we could use the original noun. I would actually say "derived from host configuration", to make it clear that we're not recycling any kind of DHCP server configuration find on the host.

+ */ +enum opt_state { + OPT_UNSET, + 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]; @@ -76,16 +88,19 @@ 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 */ + opts[i].state = OPT_UNSET;

This was needed because we were setting opts[i].state to -1. But now OPT_UNSET is 0, so you could force the assignment in the enum just to make that clear, and drop this loop.

+ + /* 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, };

Nit: if you write it like this: opts[51] = (struct opt) { 0, 4, { 0xff, 0xff, 0xff, 0xff }, 0, { 0 }, OPT_DEFAULT, }; at least the last three fields are aligned with the other options and slightly more readable, I think.

+ /* 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, }; }

-- Stefano