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daemon/c_run: maintain per session write buffers for pending data #562

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Merged
jwsbck merged 2 commits into from
Jan 12, 2026
Merged

daemon/c_run: maintain per session write buffers for pending data #562

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462479b
daemon/c_run: maintain by session write buffers for pending data
quitschbo Dec 19, 2025
6572afc
daemon/c_run: handle partial write in readloop()
quitschbo Jan 7, 2026
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79 changes: 68 additions & 11 deletions daemon/c_run.c
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Original file line number Diff line number Diff line change
Expand Up @@ -50,9 +50,10 @@
#include "container.h"
#include "cmld.h"

//TODO define in container.h?
#define CLONE_STACK_SIZE 8192

#define SESSION_WBUF_SIZE 1024

typedef struct c_run {
container_t *container;
list_t *sessions;
Expand All @@ -71,6 +72,10 @@ typedef struct c_run_session {
char *cmd;
ssize_t argc;
char **argv;
char *console_sock_container_wbuf;
int console_sock_container_wbuf_count;
char *pty_master_wbuf;
int pty_master_wbuf_count;
} c_run_session_t;

static void *
Expand Down Expand Up @@ -135,6 +140,11 @@ c_run_session_new(c_run_t *run, int create_pty, char *cmd, ssize_t argc, char **
}
session->argv[i] = NULL;

session->console_sock_container_wbuf = mem_new0(char, SESSION_WBUF_SIZE);
session->pty_master_wbuf = mem_new0(char, SESSION_WBUF_SIZE);
session->console_sock_container_wbuf_count = 0;
session->pty_master_wbuf_count = 0;

return session;
}

Expand All @@ -147,6 +157,10 @@ c_run_session_free(c_run_session_t *session)
if (session->pty_slave_name)
mem_free0(session->pty_slave_name);
mem_free_array((void *)session->argv, session->argc);
if (session->console_sock_container_wbuf)
mem_free0(session->console_sock_container_wbuf);
if (session->pty_master_wbuf)
mem_free0(session->pty_master_wbuf);
mem_free0(session);
}

Expand Down Expand Up @@ -191,6 +205,12 @@ c_run_session_cleanup(c_run_session_t *session)
shutdown(session->console_sock_container, SHUT_RDWR);
shutdown(session->console_sock_cmld, SHUT_RDWR);
}

session->console_sock_container_wbuf_count = 0;
session->pty_master_wbuf_count = 0;

mem_memset0(session->console_sock_container_wbuf, SESSION_WBUF_SIZE);
mem_memset0(session->pty_master_wbuf, SESSION_WBUF_SIZE);
}

static void
Expand Down Expand Up @@ -445,26 +465,60 @@ do_pty_exec(void *data)
}

static int
readloop(int from_fd, int to_fd)
readloop(int from_fd, int to_fd, char *buf, int *count)
{
TRACE("[EXEC] Starting read loop in process %d; from fd %d, to fd %d, PPID: %d", getpid(),
from_fd, to_fd, getppid());

int count = 0;
char buf[1024];
// write pending null
if (*count == -1) {
if (write(to_fd, "\0", 1) < 0) {
TRACE_ERRNO("[READLOOP] write failed.");
return -1;
}
*count = 0;
}

// write pending data
if (*count > 0) {
TRACE("[READLOOP] Pending %d bytes from fd: %d: %s", *count, from_fd, buf);
IF_TRUE_RETVAL(*count + 1 > SESSION_WBUF_SIZE, -1);

if (write(to_fd, buf, *count + 1) < 0) {
if (errno == EAGAIN)
return 0; // try again;
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while (0 < (count = read(from_fd, &buf, sizeof(buf) - 1))) {
buf[count] = 0;
TRACE("[READLOOP] Read %d bytes from fd: %d: %s", count, from_fd, buf);
if (write(to_fd, buf, count + 1) < 0) {
TRACE_ERRNO("[READLOOP] write failed.");
return -1;
}
}
if (count < 0 && errno != EAGAIN) {

while (0 < (*count = read(from_fd, buf, SESSION_WBUF_SIZE - 1))) {
buf[*count] = 0;
TRACE("[READLOOP] Read %d bytes from fd: %d: %s", *count, from_fd, buf);
int written = write(to_fd, buf, *count + 1);
if (written < 0) {
if (errno == EAGAIN)
return 0; // try again;
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TRACE_ERRNO("[READLOOP] write failed.");
return -1;
}
if (written == *count) {
*count = -1;
} else if (written < *count + 1) {
*count -= written;
memmove(buf, buf + written, written);
}
}
if (*count < 0 && errno != EAGAIN) {
TRACE_ERRNO("[READLOOP] read failed.");
return -1;
}

// all pending data written to to_fd, reset input/output parameter count
*count = 0;

return 0;
}

Expand All @@ -483,7 +537,9 @@ c_run_cb_read_pty(int fd, unsigned events, UNUSED event_io_t *io, void *data)
}

TRACE("Entering PTY master reading loop");
if (-1 == readloop(session->pty_master, session->console_sock_container)) {
if (-1 == readloop(session->pty_master, session->console_sock_container,
session->console_sock_container_wbuf,
&session->console_sock_container_wbuf_count)) {
ERROR("Readloop returned an error, cleanup!");
c_run_session_cleanup(session);
}
Expand All @@ -504,7 +560,8 @@ c_run_cb_write_pty(int fd, unsigned events, UNUSED event_io_t *io, void *data)
}

TRACE("Entering console sock reading loop");
if (-1 == readloop(session->console_sock_container, session->pty_master)) {
if (-1 == readloop(session->console_sock_container, session->pty_master,
session->pty_master_wbuf, &session->pty_master_wbuf_count)) {
ERROR("Readloop returned an error, cleanup!");
c_run_session_cleanup(session);
}
Expand Down