1 files changed, 122 insertions, 0 deletions
diff --git a/src/filter.c b/src/filter.c
new file mode 100644
index 0000000..7bc2a68
--- /dev/null
+++ b/src/filter.c
@@ -0,0 +1,122 @@
+#include "filter.h"
+#include "log.h"
+
+#include <assert.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <poll.h>
+#include <signal.h>
+#include <string.h>
+#include <unistd.h>
+
+#define FILTER_TIMEOUT_MS 250
+
+/* ── filter_start ────────────────────────────────────────────────────────── */
+
+void filter_start(Unit *u) {
+    assert(u != NULL);
+    assert(u->filter_in_fd == -1);
+
+    if (!u->log_filter[0]) return;
+
+    int to_filter[2], from_filter[2];
+    if (pipe(to_filter) < 0) {
+        log_warn("filter: pipe() failed for %s: %s", u->name, strerror(errno));
+        return;
+    }
+    if (pipe(from_filter) < 0) {
+        log_warn("filter: pipe() failed for %s: %s", u->name, strerror(errno));
+        close(to_filter[0]); close(to_filter[1]);
+        return;
+    }
+
+    pid_t pid = fork();
+    if (pid < 0) {
+        log_warn("filter: fork() failed for %s: %s", u->name, strerror(errno));
+        close(to_filter[0]);  close(to_filter[1]);
+        close(from_filter[0]); close(from_filter[1]);
+        return;
+    }
+
+    if (pid == 0) {
+        /* Child: wire pipes and exec the filter */
+        if (dup2(to_filter[0],   STDIN_FILENO)  < 0) _exit(1);
+        if (dup2(from_filter[1], STDOUT_FILENO) < 0) _exit(1);
+        close(to_filter[0]);  close(to_filter[1]);
+        close(from_filter[0]); close(from_filter[1]);
+        execl(u->log_filter, u->log_filter, (char *)NULL);
+        _exit(1);
+    }
+
+    /* Parent: keep write end of to_filter, read end of from_filter */
+    close(to_filter[0]);
+    close(from_filter[1]);
+    if (fcntl(from_filter[0], F_SETFL, O_NONBLOCK) < 0)
+        log_warn("filter: fcntl O_NONBLOCK failed for %s", u->name);
+
+    u->filter_pid    = pid;
+    u->filter_in_fd  = to_filter[1];
+    u->filter_out_fd = from_filter[0];
+    log_info("filter: started '%s' (pid %d) for unit %s",
+             u->log_filter, (int)pid, u->name);
+}
+
+/* ── filter_apply ────────────────────────────────────────────────────────── */
+
+void filter_apply(Unit *u, char *buf, int bufsize, int *len) {
+    assert(u != NULL);
+    assert(buf != NULL);
+    assert(len != NULL);
+
+    if (u->filter_in_fd < 0) return;
+
+    ssize_t w = write(u->filter_in_fd, buf, (size_t)*len);
+    if (w < 0) {
+        log_warn("filter: write failed for %s: %s — stopping filter",
+                 u->name, strerror(errno));
+        filter_stop(u);
+        return;
+    }
+
+    struct pollfd pfd = { u->filter_out_fd, POLLIN, 0 };
+    int r = poll(&pfd, 1, FILTER_TIMEOUT_MS);
+    if (r < 0) {
+        log_warn("filter: poll failed for %s: %s", u->name, strerror(errno));
+        return; /* pass through unchanged */
+    }
+    if (r == 0) return; /* timeout — pass through unchanged */
+
+    ssize_t n = read(u->filter_out_fd, buf, bufsize - 1);
+    if (n < 0 && errno != EAGAIN)
+        log_warn("filter: read failed for %s: %s", u->name, strerror(errno));
+    if (n > 0) {
+        buf[n] = '\0';
+        *len = (int)n;
+    } else {
+        *len = 0; /* filter suppressed all output */
+    }
+}
+
+/* ── filter_stop / filter_stop_all ───────────────────────────────────────── */
+
+void filter_stop(Unit *u) {
+    assert(u != NULL);
+
+    if (u->filter_pid <= 0) return;
+
+    close(u->filter_in_fd);
+    close(u->filter_out_fd);
+    kill(u->filter_pid, SIGTERM);
+
+    u->filter_in_fd  = -1;
+    u->filter_out_fd = -1;
+    u->filter_pid    = 0;
+    log_info("filter: stopped filter for unit %s", u->name);
+}
+
+void filter_stop_all(void) {
+    assert(g.unit_count >= 0);
+
+    for (int i = 0; i < g.unit_count; i++)
+        filter_stop(&g.units[i]);
+}