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fd-util: Expose helper to pack fds into 3,4,5,...

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This is useful for situations where an array of FDs is to be passed into
a child process (i.e. by passing it through safe_fork). This function
can be called in the child (before calling exec) to pack the FDs to all
be next to each-other starting from SD_LISTEN_FDS_START (i.e. 3)
This commit is contained in:
Adrian Vovk
2024-02-19 11:18:11 +00:00
committed by Luca Boccassi
parent 034569150f
commit 85f660d46b
6 changed files with 82 additions and 48 deletions
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src/core/exec-invoke.c
+1 -41
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@@ -66,46 +66,6 @@
#define SNDBUF_SIZE (8*1024*1024)
static int shift_fds(int fds[], size_t n_fds) {
if (n_fds <= 0)
return 0;
/* Modifies the fds array! (sorts it) */
assert(fds);
for (int start = 0;;) {
int restart_from = -1;
for (int i = start; i < (int) n_fds; i++) {
int nfd;
/* Already at right index? */
if (fds[i] == i+3)
continue;
nfd = fcntl(fds[i], F_DUPFD, i + 3);
if (nfd < 0)
return -errno;
safe_close(fds[i]);
fds[i] = nfd;
/* Hmm, the fd we wanted isn't free? Then
* let's remember that and try again from here */
if (nfd != i+3 && restart_from < 0)
restart_from = i;
}
if (restart_from < 0)
break;
start = restart_from;
}
return 0;
}
static int flag_fds(
const int fds[],
size_t n_socket_fds,
@@ -4900,7 +4860,7 @@ int exec_invoke(
r = close_all_fds(keep_fds, n_keep_fds);
if (r >= 0)
r = shift_fds(params->fds, n_fds);
r = pack_fds(params->fds, n_fds);
if (r >= 0)
r = flag_fds(params->fds, n_socket_fds, n_fds, context->non_blocking);
if (r < 0) {