From: Rafael Sadowski <rafael@sizeofvoid.org>
Subject: [1/7] relayd: convert proc.c to new imsg API
To: tech@openbsd.org
Date: Sun, 7 Jun 2026 08:57:54 +0200

This is a series of commits for an imsg APIv2 rework in relayd. These
were committed and tested individually. They can be reviewed in their
entirety here:

gothub: https://rsadowski.gothub.org/?action=summary&headref=imsg_v2&path=relayd.git
PR: https://codeberg.org/rsadowski/relayd/pulls/1/files


commit 11d91fb058229c848c44618ab0716659f0578d8c
Author: Rafael Sadowski <rafael@sizeofvoid.org>
Date:   Sat Jun 6 08:43:41 2026 +0200

    relayd: convert proc.c to new imsg API
    
    Replace IMSG_SIZE_CHECK() + memcpy() with imsg_get_data(), which does
    the length check and copy in one call. Use the imsg accessors
    (imsg_get_*) instead of touching imsg.hdr directly and
    imsgbuf_get()/imsgbuf_read() instead of imsg_get().
    
    Rewrite proc_forward_imsg() to use imsg_forward() per target imsgbuf
    instead of re-composing via proc_compose_imsg(); arm the write event
    with imsg_event_add() after each forward.
    
    proc_forward_imsg() never forwarded an fd, and imsg_forward() rewinds
    the buffer internally, so multiple forwards per message keep working.
    
    Drop the now-unused n parameter (all callers passed -1).

diff --git a/control.c b/control.c
index 2793461..6c29f2b 100644
--- a/control.c
+++ b/control.c
@@ -361,7 +361,7 @@ control_dispatch_imsg(int fd, short event, void *arg)
 			break;
 		case IMSG_CTL_SHUTDOWN:
 		case IMSG_CTL_RELOAD:
-			proc_forward_imsg(env->sc_ps, &imsg, PROC_PARENT, -1);
+			proc_forward_imsg(env->sc_ps, &imsg, PROC_PARENT);
 			break;
 		case IMSG_CTL_POLL:
 			proc_compose(env->sc_ps, PROC_HCE,
@@ -385,9 +385,9 @@ control_dispatch_imsg(int fd, short event, void *arg)
 
 			memcpy(&verbose, imsg.data, sizeof(verbose));
 
-			proc_forward_imsg(env->sc_ps, &imsg, PROC_PARENT, -1);
-			proc_forward_imsg(env->sc_ps, &imsg, PROC_HCE, -1);
-			proc_forward_imsg(env->sc_ps, &imsg, PROC_RELAY, -1);
+			proc_forward_imsg(env->sc_ps, &imsg, PROC_PARENT);
+			proc_forward_imsg(env->sc_ps, &imsg, PROC_HCE);
+			proc_forward_imsg(env->sc_ps, &imsg, PROC_RELAY);
 
 			memcpy(imsg.data, &verbose, sizeof(verbose));
 			control_imsg_forward(ps, &imsg);
diff --git a/proc.c b/proc.c
index 361f05a..d38bebd 100644
--- a/proc.c
+++ b/proc.c
@@ -599,7 +599,7 @@ proc_dispatch(int fd, short event, void *arg)
 	struct imsgbuf		*ibuf;
 	struct imsg		 imsg;
 	ssize_t			 n;
-	int			 verbose;
+	int			 ver;
 	const char		*title;
 	struct privsep_fd	 pf;
 
@@ -607,9 +607,11 @@ proc_dispatch(int fd, short event, void *arg)
 	ibuf = &iev->ibuf;
 
 	if (event & EV_READ) {
-		if ((n = imsgbuf_read(ibuf)) == -1)
+		switch (imsgbuf_read(ibuf)) {
+		case -1:
 			fatal("%s: imsgbuf_read", __func__);
-		if (n == 0) {
+			break;
+		case 0:
 			/* this pipe is dead, so remove the event handler */
 			event_del(&iev->ev);
 			event_loopexit(NULL);
@@ -630,15 +632,16 @@ proc_dispatch(int fd, short event, void *arg)
 	}
 
 	for (;;) {
-		if ((n = imsg_get(ibuf, &imsg)) == -1)
-			fatal("%s: imsg_get", __func__);
+		if ((n = imsgbuf_get(ibuf, &imsg)) == -1)
+			fatal("%s: imsgbuf_get", __func__);
 		if (n == 0)
 			break;
 
 #if DEBUG > 1
 		log_debug("%s: %s %d got imsg %d peerid %d from %s %d",
 		    __func__, title, ps->ps_instance + 1,
-		    imsg.hdr.type, imsg.hdr.peerid, p->p_title, imsg.hdr.pid);
+		    imsg_get_type(&imsg), imsg_get_id(&imsg),
+		    p->p_title, imsg_get_pid(&imsg));
 #endif
 
 		/*
@@ -653,24 +656,26 @@ proc_dispatch(int fd, short event, void *arg)
 		/*
 		 * Generic message handling
 		 */
-		switch (imsg.hdr.type) {
+		switch (imsg_get_type(&imsg)) {
 		case IMSG_CTL_VERBOSE:
-			IMSG_SIZE_CHECK(&imsg, &verbose);
-			memcpy(&verbose, imsg.data, sizeof(verbose));
-			log_setverbose(verbose);
+			if (imsg_get_data(&imsg, &ver, sizeof(ver)) == -1)
+				fatalx("%s: imsg_get_data", __func__);
+
+			log_setverbose(ver);
 			break;
 		case IMSG_CTL_PROCFD:
-			IMSG_SIZE_CHECK(&imsg, &pf);
-			memcpy(&pf, imsg.data, sizeof(pf));
+			if (imsg_get_data(&imsg, &pf, sizeof(pf)) == -1)
+				fatalx("%s: imsg_get_data", __func__);
+
 			proc_accept(ps, imsg_get_fd(&imsg), pf.pf_procid,
-			    pf.pf_instance);
+				    pf.pf_instance);
 			break;
 		default:
 			fatalx("%s: %s %d got invalid imsg %d peerid %d "
 			    "from %s %d",
 			    __func__, title, ps->ps_instance + 1,
-			    imsg.hdr.type, imsg.hdr.peerid,
-			    p->p_title, imsg.hdr.pid);
+			    imsg_get_type(&imsg), imsg_get_id(&imsg),
+			    p->p_title, imsg_get_pid(&imsg));
 		}
 		imsg_free(&imsg);
 	}
@@ -790,10 +795,18 @@ proc_composev(struct privsep *ps, enum privsep_procid id,
 
 int
 proc_forward_imsg(struct privsep *ps, struct imsg *imsg,
-    enum privsep_procid id, int n)
+    enum privsep_procid id)
 {
-	return (proc_compose_imsg(ps, id, n, imsg->hdr.type,
-	    imsg->hdr.peerid, -1, imsg->data, IMSG_DATA_SIZE(imsg)));
+	int	 m, n = -1;
+
+	proc_range(ps, id, &n, &m);
+	for (; n < m; n++) {
+		if (imsg_forward(&ps->ps_ievs[id][n].ibuf, imsg) == -1)
+			return (-1);
+		imsg_event_add(&ps->ps_ievs[id][n]);
+	}
+
+	return (0);
 }
 
 struct imsgbuf *
diff --git a/relayd.h b/relayd.h
index 5536b47..16fe2bf 100644
--- a/relayd.h
+++ b/relayd.h
@@ -1424,7 +1424,7 @@ int	 proc_composev_imsg(struct privsep *, enum privsep_procid, int,
 int	 proc_composev(struct privsep *, enum privsep_procid,
 	    uint16_t, const struct iovec *, int);
 int	 proc_forward_imsg(struct privsep *, struct imsg *,
-	    enum privsep_procid, int);
+	    enum privsep_procid);
 struct imsgbuf *
 	 proc_ibuf(struct privsep *, enum privsep_procid, int);
 struct imsgev *