On Fri, Apr 03, 2026 at 10:02:04AM +0200, Laurent Vivier wrote:
Add a --dhcp-boot option that populates the 'file' field in DHCP reply messages with the given filename.
Using --dhcp-boot together with --no-dhcp is rejected at startup.
Signed-off-by: Laurent Vivier
Reviewed-by: David Gibson
--- conf.c | 10 ++++++++++ dhcp.c | 5 ++++- passt.1 | 6 ++++++ passt.h | 1 + 4 files changed, 21 insertions(+), 1 deletion(-)
diff --git a/conf.c b/conf.c index ae37bf96dac4..2cf1bc7420d3 100644 --- a/conf.c +++ b/conf.c @@ -984,6 +984,7 @@ static void usage(const char *name, FILE *f, int status) " --no-udp Disable UDP protocol handler\n" " --no-icmp Disable ICMP/ICMPv6 protocol handler\n" " --no-dhcp Disable DHCP server\n" + " --dhcp-boot FILE DHCP boot filename option\n" " --no-ndp Disable NDP responses\n" " --no-dhcpv6 Disable DHCPv6 server\n" " --no-ra Disable router advertisements\n" @@ -1537,6 +1538,7 @@ void conf(struct ctx *c, int argc, char **argv) {"migrate-exit", no_argument, NULL, 29 }, {"migrate-no-linger", no_argument, NULL, 30 }, {"stats", required_argument, NULL, 31 }, + {"dhcp-boot", required_argument, NULL, 32 }, { 0 }, }; const char *optstring = "+dqfel:hs:F:I:p:P:m:a:n:M:g:i:o:D:S:H:461t:u:T:U:"; @@ -1775,6 +1777,11 @@ 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 32: + if (snprintf_check(c->dhcp_boot, sizeof(c->dhcp_boot), + "%s", optarg)) + die("Invalid DHCP bootfile name: %s", optarg); + break; case 'd': c->debug = 1; c->quiet = 0; @@ -2206,6 +2213,9 @@ void conf(struct ctx *c, int argc, char **argv) c->no_dhcpv6 = 1; }
+ if (c->no_dhcp && c->dhcp_boot[0]) + die("--dhcp-boot cannot be used with --no-dhcp"); + get_dns(c);
if (!*c->pasta_ifn) { diff --git a/dhcp.c b/dhcp.c index 1ff8cba9f93d..7fdb6e051dec 100644 --- a/dhcp.c +++ b/dhcp.c @@ -344,6 +344,9 @@ int dhcp(const struct ctx *c, struct iov_tail *data) m->op != BOOTREQUEST) return -1;
+ static_assert(sizeof(reply.file) == sizeof(c->dhcp_boot), + "dhcp_boot must have the same size as reply.file"); + reply.op = BOOTREPLY; reply.htype = m->htype; reply.hlen = m->hlen; @@ -357,7 +360,7 @@ int dhcp(const struct ctx *c, struct iov_tail *data) reply.giaddr = m->giaddr; memcpy(&reply.chaddr, m->chaddr, sizeof(reply.chaddr)); memset(&reply.sname, 0, sizeof(reply.sname)); - memset(&reply.file, 0, sizeof(reply.file)); + memcpy(&reply.file, c->dhcp_boot, sizeof(reply.file)); reply.magic = m->magic;
for (i = 0; i < ARRAY_SIZE(opts); i++) diff --git a/passt.1 b/passt.1 index 13e8df9de9f3..a6ac2884bf3f 100644 --- a/passt.1 +++ b/passt.1 @@ -342,6 +342,12 @@ Disable the DHCP server. DHCP client requests coming from guest or target namespace will be silently dropped. Implied if there is no gateway on the selected IPv4 default route.
+.TP +.BR \-\-dhcp-boot " " \fIfile +Set the boot filename in DHCP replies to \fIfile\fR. This populates the +\fIfile\fR field in BOOTP/DHCP reply messages, which can be used for +network booting (PXE). Cannot be used with \fB--no-dhcp\fR. + .TP .BR \-\-no-ndp Disable Neighbor Discovery. NDP messages coming from guest or target diff --git a/passt.h b/passt.h index 62b8dcdf0a41..4044a4c07ea3 100644 --- a/passt.h +++ b/passt.h @@ -255,6 +255,7 @@ struct ctx {
char hostname[PASST_MAXDNAME]; char fqdn[PASST_MAXDNAME]; + char dhcp_boot[128];
int ifi6; struct ip6_ctx ip6; -- 2.53.0
-- David Gibson (he or they) | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you, not the other way | around. http://www.ozlabs.org/~dgibson