[src/trunk]: src/sys/net Don't use the stack, print to the buffer directly (t...

[christos <christos%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/f44e0ed1091b
branches:  trunk
changeset: 379322:f44e0ed1091b
user:      christos <christos%NetBSD.org@localhost>
date:      Thu May 27 13:36:33 2021 +0000

description:
Don't use the stack, print to the buffer directly (this was one of the
biggest stack users).

diffstat:

 sys/net/dl_print.c |  60 +++++++++++++++++++++++++++++++++++++++--------------
 1 files changed, 44 insertions(+), 16 deletions(-)

diffs (115 lines):

diff -r 67b4cf948fdf -r f44e0ed1091b sys/net/dl_print.c
--- a/sys/net/dl_print.c        Thu May 27 13:32:54 2021 +0000
+++ b/sys/net/dl_print.c        Thu May 27 13:36:33 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: dl_print.c,v 1.6 2019/04/30 20:56:32 kre Exp $ */
+/*     $NetBSD: dl_print.c,v 1.7 2021/05/27 13:36:33 christos Exp $    */
 
 /*-
  * Copyright (c) 2014 The NetBSD Foundation, Inc.
@@ -29,17 +29,17 @@
 #include <sys/types.h>
 
 #ifdef _KERNEL
-__KERNEL_RCSID(0, "$NetBSD: dl_print.c,v 1.6 2019/04/30 20:56:32 kre Exp $");
+__KERNEL_RCSID(0, "$NetBSD: dl_print.c,v 1.7 2021/05/27 13:36:33 christos Exp $");
 #include <sys/systm.h>
 #else
-__RCSID("$NetBSD: dl_print.c,v 1.6 2019/04/30 20:56:32 kre Exp $");
+__RCSID("$NetBSD: dl_print.c,v 1.7 2021/05/27 13:36:33 christos Exp $");
 #include <stdio.h>
 static const char hexdigits[] = "0123456789abcdef";
 #endif
 #include <net/if_dl.h>
 
-char *
-lla_snprintf(char *dst, size_t dst_len, const void *src, size_t src_len)
+static int
+lla_snprintf1(char *dst, size_t dst_len, const void *src, size_t src_len)
 {
        char *dp;
        const uint8_t *sp, *ep;
@@ -47,44 +47,72 @@ lla_snprintf(char *dst, size_t dst_len, 
        if (src_len == 0 || dst_len < 3) {
                if (dst_len != 0)
                        dst[0] = '\0';
-               return NULL;
+               return src_len ? (int)(src_len * 3) - 1 : 0;
        }
 
        dp = dst;
        sp = (const uint8_t *)src;
        ep = sp + src_len;
        while (sp < ep) {
-               if (dst_len < 3)
+               if (dst_len-- == 0)
                        break;
-               dst_len -= 3;
                *dp++ = hexdigits[(*sp) >> 4];
+               if (dst_len-- == 0)
+                       break;
                *dp++ = hexdigits[(*sp++) & 0xf];
+               if (dst_len-- == 0)
+                       break;
                *dp++ = ':';
        }
-       *--dp = 0;
+       *--dp = '\0';
+
+       return (int)(src_len * 3) - 1;
+}
 
+char *
+lla_snprintf(char *dst, size_t dst_len, const void *src, size_t src_len)
+{
+       if (lla_snprintf1(dst, dst_len, src, src_len) == -1)
+               return NULL;
        return dst;
 }
 
+#define clip(a, b) ((a) > (size_t)(b) ? (a) - (size_t)(b) : 0)
+
 int
 dl_print(char *buf, size_t len, const struct dl_addr *dl)
 {
-       char abuf[256 * 3];
+       int l = snprintf(buf, len, "%.*s/%hhu#",
+           (int)dl->dl_nlen, dl->dl_data, dl->dl_type);
+       if (l == -1)
+               return l;
+       int ll = lla_snprintf1(buf + l, clip(len, l),
+           dl->dl_data + dl->dl_nlen, dl->dl_alen);
+       if (ll == -1)
+               return ll;
 
-       lla_snprintf(abuf, sizeof(abuf), dl->dl_data+dl->dl_nlen, dl->dl_alen);
-       return snprintf(buf, len, "%.*s/%hhu#%s",
-           (int)dl->dl_nlen, dl->dl_data, dl->dl_type, abuf);
+       return ll + l;
 }
 
 int
 sdl_print(char *buf, size_t len, const void *v)
 {
        const struct sockaddr_dl *sdl = v;
-       char abuf[LINK_ADDRSTRLEN];
 
        if (sdl->sdl_slen == 0 && sdl->sdl_nlen == 0 && sdl->sdl_alen == 0)
                return snprintf(buf, len, "link#%hu", sdl->sdl_index);
 
-       dl_print(abuf, sizeof(abuf), &sdl->sdl_addr);
-       return snprintf(buf, len, "[%s]:%hu", abuf, sdl->sdl_index);
+       if (len > 0) {
+               buf[0] = '[';
+               len--;
+       }
+       int l = dl_print(buf + 1, len, &sdl->sdl_addr);
+       if (l == -1)
+               return l;
+       l++;
+       len++;
+       int ll = snprintf(buf + l, clip(len, l), "]:%hu", sdl->sdl_index);
+       if (ll == -1)
+               return ll;
+       return ll + l;
 }