bgpd mrt use ibuf instead of fixed buffer

[Claudio Jeker]

Switch mrt_dump_entry_v2() to use a dynamic ibuf for the prefix and
switch the order of operation so that the memmove() of pbuf is no longer
needed. Using a static buffer is problematic when flowspec support is
added since flowspec "prefixes" can be more than 255 bytes long.

-- 
:wq Claudio

Index: mrt.c
===================================================================
RCS file: /cvs/src/usr.sbin/bgpd/mrt.c,v
retrieving revision 1.111
diff -u -p -r1.111 mrt.c
--- mrt.c       28 Dec 2022 21:30:16 -0000      1.111
+++ mrt.c       28 Mar 2023 08:30:33 -0000
@@ -688,19 +688,14 @@ fail:
 int
 mrt_dump_entry_v2(struct mrt *mrt, struct rib_entry *re, uint32_t snum)
 {
-       char             pbuf[260];
-       struct ibuf     *hbuf = NULL, *nbuf = NULL, *apbuf = NULL;
+       struct ibuf     *hbuf = NULL, *nbuf = NULL, *apbuf = NULL, *pbuf;
        struct bgpd_addr addr;
        size_t           hlen, len;
        uint16_t         subtype, apsubtype, nump, apnump, afi;
        uint8_t          safi;
-       int              plen;
 
-       pt_getaddr(re->prefix, &addr);
-       plen = prefix_write(pbuf, sizeof(pbuf), &addr, re->prefix->prefixlen,
-           0);
-       if (plen == -1) {
-               log_warnx("%s: prefix_write error", __func__);
+       if ((pbuf = ibuf_dynamic(0, UINT_MAX)) == NULL) {
+               log_warn("%s: ibuf_dynamic", __func__);
                return -1;
        }
 
@@ -724,15 +719,19 @@ mrt_dump_entry_v2(struct mrt *mrt, struc
                apsubtype = MRT_DUMP_V2_RIB_GENERIC_ADDPATH;
                aid2afi(re->prefix->aid, &afi, &safi);
 
-               /* prepend 3-bytes AFI/SAFI */
-               memmove(pbuf + 3, pbuf, plen);
-               plen += 3;
-               afi = ntohs(afi);
-               memcpy(pbuf, &afi, sizeof(afi));
-               pbuf[2] = safi;
+               /* first add 3-bytes AFI/SAFI */
+               DUMP_SHORT(pbuf, afi);
+               DUMP_BYTE(pbuf, safi);
                break;
        }
-       hlen = sizeof(snum) + sizeof(nump) + plen;
+
+       pt_getaddr(re->prefix, &addr);
+       if (prefix_writebuf(pbuf, &addr, re->prefix->prefixlen) == -1) {
+               log_warnx("%s: prefix_writebuf error", __func__);
+               goto fail;
+       }
+
+       hlen = sizeof(snum) + sizeof(nump) + ibuf_size(pbuf);
 
        if (mrt_dump_entry_v2_rib(re, &nbuf, &apbuf, &nump, &apnump))
                goto fail;
@@ -744,7 +743,7 @@ mrt_dump_entry_v2(struct mrt *mrt, struc
                        goto fail;
 
                DUMP_LONG(hbuf, snum);
-               if (ibuf_add(hbuf, pbuf, plen) == -1) {
+               if (ibuf_add(hbuf, pbuf->buf, ibuf_size(pbuf)) == -1) {
                        log_warn("%s: ibuf_add error", __func__);
                        goto fail;
                }
@@ -763,7 +762,7 @@ mrt_dump_entry_v2(struct mrt *mrt, struc
                        goto fail;
 
                DUMP_LONG(hbuf, snum);
-               if (ibuf_add(hbuf, pbuf, plen) == -1) {
+               if (ibuf_add(hbuf, pbuf->buf, ibuf_size(pbuf)) == -1) {
                        log_warn("%s: ibuf_add error", __func__);
                        goto fail;
                }
@@ -775,11 +774,13 @@ mrt_dump_entry_v2(struct mrt *mrt, struc
                apbuf = NULL;
        }
 
+       ibuf_free(pbuf);
        return (0);
 fail:
        ibuf_free(apbuf);
        ibuf_free(nbuf);
        ibuf_free(hbuf);
+       ibuf_free(pbuf);
        return (-1);
 }