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varlink: don't allocate fd control buffer on each read()

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We'll need this on each read() again, hence let's just allocate this
once and then reuse it for subsequent read()s.

Follow-up for: #28639
This commit is contained in:
Lennart Poettering
2023-08-07 20:57:45 +01:00
committed by Luca Boccassi
parent b57e752220
commit 3c8680585c
1 changed files with 17 additions and 6 deletions
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src/shared/varlink.c
+17 -6
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@@ -133,6 +133,9 @@ struct Varlink {
size_t input_buffer_size;
size_t input_buffer_unscanned;
void *input_control_buffer;
size_t input_control_buffer_size;
char *output_buffer; /* valid data starts at output_buffer_index, ends at output_buffer_index+output_buffer_size */
size_t output_buffer_index;
size_t output_buffer_size;
@@ -457,6 +460,9 @@ static void varlink_clear(Varlink *v) {
v->input_buffer = mfree(v->input_buffer);
v->output_buffer = v->output_buffer_sensitive ? erase_and_free(v->output_buffer) : mfree(v->output_buffer);
v->input_control_buffer = mfree(v->input_control_buffer);
v->input_control_buffer_size = 0;
varlink_clear_current(v);
close_many(v->output_fds, v->n_output_fds);
@@ -633,7 +639,6 @@ static int varlink_write(Varlink *v) {
#define VARLINK_FDS_MAX (16U*1024U)
static int varlink_read(Varlink *v) {
_cleanup_free_ struct cmsghdr *cmsg_fds = NULL;
struct iovec iov;
struct msghdr mh;
size_t rs;
@@ -687,16 +692,22 @@ static int varlink_read(Varlink *v) {
if (v->allow_fd_passing_input) {
iov = IOVEC_MAKE(p, rs);
/* Allocate the fd buffer on the heap, since we need a lot of space potentially */
if (!v->input_control_buffer) {
v->input_control_buffer_size = CMSG_SPACE(sizeof(int) * VARLINK_FDS_MAX);
v->input_control_buffer = malloc(v->input_control_buffer_size);
if (!v->input_control_buffer)
return -ENOMEM;
}
mh = (struct msghdr) {
.msg_iov = &iov,
.msg_iovlen = 1,
.msg_control = v->input_control_buffer,
.msg_controllen = v->input_control_buffer_size,
};
mh.msg_controllen = CMSG_SPACE(sizeof(int) * VARLINK_FDS_MAX);
mh.msg_control = cmsg_fds = malloc(mh.msg_controllen);
if (!cmsg_fds)
return -ENOMEM;
n = recvmsg_safe(v->fd, &mh, MSG_DONTWAIT|MSG_CMSG_CLOEXEC);
} else {
bool prefer_read = v->prefer_read_write;