Introduce the --dhcp-opt flag that allows setting arbitrary DHCP
options from command-line in the form of [Option CODE,VALUE].
This patch adds the option storage in struct ctx and CLI parsing;
the type-aware value parser and DHCP reply injection follow
in subsequent patches.
Link: https://bugs.passt.top/show_bug.cgi?id=192
Signed-off-by: Anshu Kumari
---
v3:
- Added dhcp_add_option() helper in dhcp.c for storing options with
duplicate-code detection.
- case 33 now calls dhcp_add_option() instead of inline storage.
v2:
- Added kerneldoc for @custom_opts, @custom_opts.code, @custom_opts.str, and @custom_opts_count in struct ctx
- Removed len and val[255] fields from struct (moved to patch 3)
- Removed braces from case 33, moved declarations (optcode, comma, end) to function scope
- Renamed code → optcode to follow function-scope convention.
---
conf.c | 24 +++++++++++++++++++++++-
dhcp.c | 38 ++++++++++++++++++++++++++++++++++++++
dhcp.h | 1 +
passt.h | 12 ++++++++++++
4 files changed, 74 insertions(+), 1 deletion(-)
diff --git a/conf.c b/conf.c
index 029b9c7..ce78af1 100644
--- a/conf.c
+++ b/conf.c
@@ -47,6 +47,7 @@
#include "lineread.h"
#include "isolation.h"
#include "log.h"
+#include "dhcp.h"
#include "vhost_user.h"
#include "epoll_ctl.h"
#include "conf.h"
@@ -616,7 +617,8 @@ static void usage(const char *name, FILE *f, int status)
" -S, --search LIST Space-separated list, search domains\n"
" a single, empty option disables the DNS search list\n"
" -H, --hostname NAME Hostname to configure client with\n"
- " --fqdn NAME FQDN to configure client with\n");
+ " --fqdn NAME FQDN to configure client with\n"
+ " --dhcp-opt CODE,VAL Set DHCP option by code\n");
if (strstr(name, "pasta"))
FPRINTF(f, " default: don't use any search list\n");
else
@@ -844,6 +846,10 @@ static void conf_print(const struct ctx *c)
info(" router: %s",
inet_ntop(AF_INET, &c->ip4.guest_gw,
buf, sizeof(buf)));
+ for (i = 0; i < c->custom_opts_count; i++)
+ info(" option %u: %s",
+ c->custom_opts[i].code,
+ c->custom_opts[i].str);
}
for (i = 0; i < ARRAY_SIZE(c->ip4.dns); i++) {
@@ -1233,6 +1239,7 @@ void conf(struct ctx *c, int argc, char **argv)
{"migrate-no-linger", no_argument, NULL, 30 },
{"stats", required_argument, NULL, 31 },
{"conf-path", required_argument, NULL, 'c' },
+ {"dhcp-opt", required_argument, NULL, 33 },
{ 0 },
};
const char *optstring = "+dqfel:hs:c:F:I:p:P:m:a:n:M:g:i:o:D:S:H:461t:u:T:U:";
@@ -1248,10 +1255,13 @@ void conf(struct ctx *c, int argc, char **argv)
uint8_t prefix_len_from_opt = 0;
unsigned int ifi4 = 0, ifi6 = 0;
const char *logfile = NULL;
+ unsigned long optcode;
char *runas = NULL;
size_t logsize = 0;
+ const char *comma;
long fd_tap_opt;
int name, ret;
+ char *end;
uid_t uid;
gid_t gid;
@@ -1465,6 +1475,18 @@ void conf(struct ctx *c, int argc, char **argv)
die("Can't display statistics if not running in foreground");
c->stats = strtol(optarg, NULL, 0);
break;
+ case 33:
+ comma = strchr(optarg, ',');
+ if (!comma)
+ die("--dhcp-opt requires CODE,VALUE format");
+
+ optcode = strtoul(optarg, &end, 0);
+ if (end != comma || optcode < 1 || optcode > 254)
+ die("DHCP option code must be 1-254: %s",
+ optarg);
+
+ dhcp_add_option(c, optcode, comma + 1);
+ break;
case 'd':
c->debug = 1;
c->quiet = 0;
diff --git a/dhcp.c b/dhcp.c
index 1ff8cba..c5fbf37 100644
--- a/dhcp.c
+++ b/dhcp.c
@@ -33,6 +33,44 @@
#include "log.h"
#include "dhcp.h"
+
+/**
+ * dhcp_add_option() - Add or update a custom DHCP option
+ * @c: Execution context
+ * @code: DHCP option code
+ * @val_str: Value string from command line
+ *
+ * If @code was already added, the previous value is overwritten.
+ * Calls die() on any error.
+ *
+ * Return: 0 on success
+ */
+int dhcp_add_option(struct ctx *c, uint8_t code, const char *val_str)
+{
+ int idx;
+
+ for (idx = 0; idx < c->custom_opts_count; idx++) {
+ if (c->custom_opts[idx].code == code)
+ break;
+ }
+
+ if (idx == c->custom_opts_count) {
+ if (c->custom_opts_count >= MAX_CUSTOM_DHCP_OPTS)
+ die("Too many --dhcp-opt entries (max %d)",
+ MAX_CUSTOM_DHCP_OPTS);
+ c->custom_opts_count++;
+ }
+
+ c->custom_opts[idx].code = code;
+
+ if (snprintf_check(c->custom_opts[idx].str,
+ sizeof(c->custom_opts[0].str),
+ "%s", val_str))
+ die("DHCP option value too long: %s", val_str);
+
+ return 0;
+}
+
/**
* struct opt - DHCP option
* @sent: Convenience flag, set while filling replies
diff --git a/dhcp.h b/dhcp.h
index cd50c99..9c8f1e3 100644
--- a/dhcp.h
+++ b/dhcp.h
@@ -8,5 +8,6 @@
int dhcp(const struct ctx *c, struct iov_tail *data);
void dhcp_init(void);
+int dhcp_add_option(struct ctx *c, uint8_t code, const char *val_str);
#endif /* DHCP_H */
diff --git a/passt.h b/passt.h
index 1726965..3a0816f 100644
--- a/passt.h
+++ b/passt.h
@@ -182,6 +182,10 @@ struct ip6_ctx {
* @dns_search: DNS search list
* @hostname: Guest hostname
* @fqdn: Guest FQDN
+ * @custom_opts: User-specified DHCP options from --dhcp-opt
+ * @custom_opts.code: DHCP option code
+ * @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
* @ip6: IPv6 configuration
* @pasta_ifn: Name of namespace interface for pasta
@@ -263,6 +267,14 @@ struct ctx {
char hostname[PASST_MAXDNAME];
char fqdn[PASST_MAXDNAME];
+#define MAX_CUSTOM_DHCP_OPTS 32
+
+ struct {
+ uint8_t code;
+ char str[256];
+ } custom_opts[MAX_CUSTOM_DHCP_OPTS];
+ int custom_opts_count;
+
int ifi6;
struct ip6_ctx ip6;
--
2.54.0