dump_cache truncates large records

[ialexiad]

Describe the bug
When dumping the unbound cache, some large records are truncated and there is no newline between those and the next rrset entry, resulting in a corrupt dump file, that cannot be loaded back to unbound.

To reproduce
Steps to reproduce the behavior:

1. Make a DNS request for a large entry, e.g. the TXT record for _p.3.1o586rh._u.taylorandfrancis.com._spf.smart.ondmarc.com. The answer currently is something like:

_p.3.1o586rh._u.taylorandfrancis.com._spf.smart.ondmarc.com.	86400	IN	TXT	"v=spf1 ip4:41.74.192.0/21 ip4:87.238.80.0/21 ip4:108.177.8.0/21 ip4:148.105.8.0/21 ip4:172.253.56.0/21 ip4:199.122.120.0/21 ip4:13.110.216.0/22 ip4:52.82.172.0/22 ip4:130.211.0.0/22 ip4:199.127.232.0/22 ip4:199.255.192.0/22 ip4:41.74.200.0/23 ip4:41.74." "204.0/23 ip4:64.132.88.0/23 ip4:69.63.150.0/23 ip4:159.92.154.0/23 ip4:159.92.158.0/23 ip4:170.10.128.0/23 ip4:35.190.247.0/24 ip4:41.74.206.0/24 ip4:51.163.158.0/24 ip4:62.140.7.0/24 ip4:63.128.21.0/24 ip4:64.132.92.0/24 ip4:70.33.179.0/24 ip4:91.220.4" "2.0/24 ip4:103.13.69.0/24 ip4:103.96.21.0/24 ip4:103.96.23.0/24 ip4:124.47.150.0/24 ip4:124.47.189.0/24 ip4:146.101.78.0/24 ip4:147.28.36.0/24 ip4:159.92.157.0/24 ip4:170.10.133.0/24 ip4:176.32.105.0/24 ip4:176.32.127.0/24 ip4:180.189.28.0/24 ip4:185.58" ".85.0/24 ip4:185.58.86.0/24 ip4:192.69.130.0/24 ip4:194.104.109.0/24 ip4:194.104.111.0/24 ip4:195.130.217.0/24 ip4:203.81.17.0/24 ip4:205.139.110.0/24 ip4:207.67.38.0/24 ip4:207.82.80.0/24 ip4:207.250.68.0/24 ip4:212.11.79.0/24 ip4:216.145.217.0/24 ip4:" "216.145.221.0/24 ip4:216.205.24.0/24 include:_p.4.1o586rh._u.taylorandfrancis.com._spf.smart.ondmarc.com ~all"

2. Dump the unbound cache to a file and look for the rrset for _p.3.1o586rh._u.taylorandfrancis.com._spf.smart.ondmarc.com. . The entry will be truncated with the next ;rrset appended to it, like:

;rrset 84568 1 0 8 2
_p.3.1o586rh._u.taylorandfrancis.com._spf.smart.ondmarc.com.    84568   IN      TXT     "v=spf1 ip4:41.74.192.0/21 ip4:87.238.80.0/21 ip4:108.177.8.0/21 ip4:148.105.8.0/21 ip4:172.253.56.0/21 ip4:199.122.120.0/21 ip4:13.110.216.0/22 ip4:52.82.172.0/22 ip4:130.211.0.0/22 ip4:199.127.232.0/22 ip4:199.255.192.0/22 ip4:41.74.200.0/23 ip4:41.74." "204.0/23 ip4:64.132.88.0/23 ip4:69.63.150.0/23 ip4:159.92.154.0/23 ip4:159.92.158.0/23 ip4:170.10.128.0/23 ip4:35.190.247.0/24 ip4:41.74.206.0/24 ip4:51.163.158.0/24 ip4:62.140.7.0/24 ip4:63.128.21.0/24 ip4:64.132.92.0/24 ip4:70.33.179.0/24 ip4:91.220.4" "2.0/24 ip4:103.13.69.0/24 ip4:103.96.21.0/24 ip4:103.96.23.0/24 ip4:124.47.150.0/24 ip4:124.47.189.0/24 ip4:146.101.78.0/24 ip4:147.28.36.0/24 ip4:159.92.157.0/24 ip4:170.10.133.0/24 ip4:176.32.105.0/24 ip4:176.32.127.0/24 ip4:180.189.28.0/24 ip4:185.58" ".85.0/24 ip4:185.58.86.0/24 ip4:192.69.130.0/24 ip4:194.104.109.0/24 ip4:194.104.111.0/24 ip4:195.130.217.0/24 ip4:203.81.17.0/24 ip4:205.139.110.0/24 ip4:207.67.38.0/24 ip4:207.82;rrset 84568 3 0 1 0
dion.ns.cloudflare.com. 84568   IN      AAAA    2606:4700:58::adf5:3b9c
dion.ns.cloudflare.com. 84568   IN      AAAA    2803:f800:50::6ca2:c19c
dion.ns.cloudflare.com. 84568   IN      AAAA    2a06:98c1:50::ac40:219c

3. Attempting to load this cache file back into unbound, results in the following error messages:

unbound[22:0] warning: error expected ';rrset' but got dion.ns.cloudflare.com.     84568      IN      AAAA    2606:4700:58::adf5:3b9c
unbound-control[46:0] fatal error: could not recv: Connection reset by peer

System:

• Unbound version: 1.19
• OS: alpine linux 3.19 docker container
• unbound -V output:

Version 1.19.0

Configure line: --build=x86_64-alpine-linux-musl --host=x86_64-alpine-linux-musl --prefix=/usr --sysconfdir=/etc --mandir=/usr/share/man --localstatedir=/var --with-username=unbound --with-run-dir= --with-pidfile= --with-rootkey-file=/usr/share/dnssec-root/trusted-key.key --with-libevent --with-pthreads --disable-static --disable-rpath --enable-dnstap --with-ssl --without-pythonmodule --with-pyunbound
Linked libs: libevent 2.1.12-stable (it uses epoll), OpenSSL 3.1.4 24 Oct 2023
Linked modules: dns64 respip validator iterator