From aa1cc8922867b8f7c17742f8da3b9fcc6291bbeb Mon Sep 17 00:00:00 2001
From: Alyssa Ross <hi@alyssa.is>
Date: Sat, 26 Apr 2025 10:44:25 +0200
Subject: [PATCH] conf: allow --fd 0
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inetd-style socket passing traditionally starts a service with a
connected socket on file descriptors 0 and 1. passt disallowing
obtaining its socket from either of these descriptors made it
difficult to use with super-servers providing this interface — in my
case I wanted to use passt with s6-ipcserver[1]. Since (as far as I
can tell) passt does not use standard input for anything else (unlike
standard output), it should be safe to relax the restrictions on --fd
to allow setting it to 0, enabling this use case.
Link: https://skarnet.org/software/s6/s6-ipcserver.html [1]
Signed-off-by: Alyssa Ross <hi@alyssa.is>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
---
conf.c | 3 ++-
util.c | 4 +++-
2 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/conf.c b/conf.c
index f942851..a6d7e22 100644
--- a/conf.c
+++ b/conf.c
@@ -1717,7 +1717,8 @@ void conf(struct ctx *c, int argc, char **argv)
fd_tap_opt = strtol(optarg, NULL, 0);
if (errno ||
- fd_tap_opt <= STDERR_FILENO || fd_tap_opt > INT_MAX)
+ (fd_tap_opt != STDIN_FILENO && fd_tap_opt <= STDERR_FILENO) ||
+ fd_tap_opt > INT_MAX)
die("Invalid --fd: %s", optarg);
c->fd_tap = fd_tap_opt;
diff --git a/util.c b/util.c
index 62a6003..f5497d4 100644
--- a/util.c
+++ b/util.c
@@ -875,7 +875,9 @@ void close_open_files(int argc, char **argv)
errno = 0;
fd = strtol(optarg, NULL, 0);
- if (errno || fd <= STDERR_FILENO || fd > INT_MAX)
+ if (errno ||
+ (fd != STDIN_FILENO && fd <= STDERR_FILENO) ||
+ fd > INT_MAX)
die("Invalid --fd: %s", optarg);
}
} while (name != -1);