When sending via UDP, syslogd(8) can use iovec with sendmsg(2)

instead of copying the strings with snprintf(3).
OK martijn@

diff --git a/usr.sbin/syslogd/syslogd.c b/usr.sbin/syslogd/syslogd.c
index e6b6b94..aa00d24 100644 (file)
--- a/usr.sbin/syslogd/syslogd.c
+++ b/usr.sbin/syslogd/syslogd.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: syslogd.c,v 1.271 2021/10/24 21:24:19 deraadt Exp $   */
+/*     $OpenBSD: syslogd.c,v 1.272 2021/11/10 21:59:47 bluhm Exp $     */
 
 /*
  * Copyright (c) 2014-2021 Alexander Bluhm <bluhm@genua.de>
@@ -1895,6 +1895,7 @@ void
 fprintlog(struct filed *f, int flags, char *msg)
 {
        struct iovec iov[IOVCNT], *v;
+       struct msghdr msghdr;
        int l, retryonce;
        char line[LOG_MAXLINE + 1], pribuf[13], greetings[500], repbuf[80];
        char ebuf[ERRBUFSIZE];
@@ -2035,20 +2036,22 @@ fprintlog(struct filed *f, int flags, char *msg)
 
        case F_FORWUDP:
                log_debug(" %s", f->f_un.f_forw.f_loghost);
-               l = snprintf(line, MINIMUM(MAX_UDPMSG + 1, sizeof(line)),
-                   "%s%s%s%s%s%s%s", (char *)iov[0].iov_base,
-                   (char *)iov[1].iov_base, (char *)iov[2].iov_base,
-                   (char *)iov[3].iov_base, (char *)iov[4].iov_base,
-                   (char *)iov[5].iov_base, (char *)iov[6].iov_base);
-               if (l < 0)
-                       l = strlcpy(line, iov[5].iov_base, sizeof(line));
-               if (l >= sizeof(line))
-                       l = sizeof(line) - 1;
-               if (l >= MAX_UDPMSG + 1)
-                       l = MAX_UDPMSG;
-               if (sendto(f->f_file, line, l, 0,
-                   (struct sockaddr *)&f->f_un.f_forw.f_addr,
-                   f->f_un.f_forw.f_addr.ss_len) != l) {
+               l = iov[0].iov_len + iov[1].iov_len + iov[2].iov_len +
+                   iov[3].iov_len + iov[4].iov_len + iov[5].iov_len +
+                   iov[6].iov_len;
+               if (l > MAX_UDPMSG) {
+                       l -= MAX_UDPMSG;
+                       if (iov[5].iov_len > l)
+                               iov[5].iov_len -= l;
+                       else
+                               iov[5].iov_len = 0;
+               }
+               memset(&msghdr, 0, sizeof(msghdr));
+               msghdr.msg_name = &f->f_un.f_forw.f_addr;
+               msghdr.msg_namelen = f->f_un.f_forw.f_addr.ss_len;
+               msghdr.msg_iov = iov;
+               msghdr.msg_iovlen = IOVCNT;
+               if (sendmsg(f->f_file, &msghdr, 0) == -1) {
                        switch (errno) {
                        case EADDRNOTAVAIL:
                        case EHOSTDOWN:
@@ -2061,7 +2064,7 @@ fprintlog(struct filed *f, int flags, char *msg)
                                break;
                        default:
                                f->f_type = F_UNUSED;
-                               log_warn("sendto \"%s\"",
+                               log_warn("sendmsg to \"%s\"",
                                    f->f_un.f_forw.f_loghost);
                                break;
                        }