HTTP/3 UDP socket leak leads to local port exhaustion after 0-RTT rejected

I am running `dnsproxy` on Linux AMD64 as follows:
```
2026/07/17 15:38:38.355881 INFO dnsproxy starting version=v0.83.0 revision=d020fcc62cfd62958706295d7c9d9e82ae015f52 branch=v0.83.0 commit_time=1783069482

dnsproxy -l 127.0.0.6 -u h3://dns.google/dns-query -b 8.8.8.8:53
```

This setup has been working well for many months, however today I began to get `0-RTT rejected` responses from Google DNS:
```
Jul 17 15:36:14 dnsproxy[436873]: 2026/07/17 15:36:14.221298 ERROR exchange failed prefix=dnsproxy upstream=https://dns.google:443/dns-query question=";accounts.google.com.\tIN\t A" duration=26.777927ms err="exchanging: requesting https://dns.google:443/dns-query: Get_0rtt \"https://dns.google:443/dns-query?dns=AAABEAABAAAAAAABCGFjY291bnRzBmdvb2dsZQNjb20AAAEAAQAAKQTQAACAAAAA\": http3: parsing frame failed: 0-RTT rejected"
Jul 17 15:36:14 dnsproxy[436873]: 2026/07/17 15:36:14.227267 ERROR exchange failed prefix=dnsproxy upstream=https://dns.google:443/dns-query question=";history.l.google.com.\tIN\t HTTPS" duration=12.137872ms err="exchanging: requesting https://dns.google:443/dns-query: Get_0rtt \"https://dns.google:443/dns-query?dns=AAABEAABAAAAAAABB2hpc3RvcnkBbAZnb29nbGUDY29tAABBAAEAACkE0AAAgAAAAA\": http3: parsing frame failed: 0-RTT rejected"
Jul 17 15:36:14 dnsproxy[436873]: 2026/07/17 15:36:14.423144 ERROR exchange failed prefix=dnsproxy upstream=https://dns.google:443/dns-query question=";2-prod-dynamite-prod-02-us-signaler-pa.clients6.google.com.\tIN\t HTTPS" duration=16.508161ms err="exchanging: requesting https://dns.google:443/dns-query: Get_0rtt \"https://dns.google:443/dns-query?dns=AAABEAABAAAAAAABJjItcHJvZC1keW5hbWl0ZS1wcm9kLTAyLXVzLXNpZ25hbGVyLXBhCGNsaWVudHM2Bmdvb2dsZQNjb20AAEEAAQAAKQTQAACAAAAA\": http3: parsing frame failed: 0-RTT rejected"
Jul 17 15:36:15 dnsproxy[436873]: 2026/07/17 15:36:15.542314 ERROR exchange failed prefix=dnsproxy upstream=https://dns.google:443/dns-query question=";mail.google.com.\tIN\t A" duration=28.740321ms err="exchanging: requesting https://dns.google:443/dns-query: Get_0rtt \"https://dns.google:443/dns-query?dns=AAABEAABAAAAAAABBG1haWwGZ29vZ2xlA2NvbQAAAQABAAApBNAAAIAAAAA\": http3: parsing frame failed: 0-RTT rejected"
Jul 17 15:36:15 dnsproxy[436873]: 2026/07/17 15:36:15.542355 ERROR exchange failed prefix=dnsproxy upstream=https://dns.google:443/dns-query question=";mail.google.com.\tIN\t HTTPS" duration=28.834902ms err="exchanging: requesting https://dns.google:443/dns-query: Get_0rtt \"https://dns.google:443/dns-query?dns=AAABEAABAAAAAAABBG1haWwGZ29vZ2xlA2NvbQAAQQABAAApBNAAAIAAAAA\": http3: parsing frame failed: 0-RTT rejected"
```

After such responses, dnsproxy seems to open / leak a number of new UDP sockets:
```
# lsof -p 436873
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
dnsproxy 436873 dnsproxy-google cwd DIR 254,1 4096 2 /
dnsproxy 436873 dnsproxy-google rtd DIR 254,1 4096 2 /
dnsproxy 436873 dnsproxy-google txt REG 254,1 11935906 8782474 /opt/dnsproxy/dnsproxy
dnsproxy 436873 dnsproxy-google 0r CHR 1,3 0t0 4 /dev/null
dnsproxy 436873 dnsproxy-google 1u unix 0x000000007c9226f4 0t0 365483103 type=STREAM (CONNECTED)
dnsproxy 436873 dnsproxy-google 2u unix 0x000000007c9226f4 0t0 365483103 type=STREAM (CONNECTED)
dnsproxy 436873 dnsproxy-google 3r REG 0,27 0 293214 /sys/fs/cgroup/system.slice/dnsproxy-google.service/cpu.max
dnsproxy 436873 dnsproxy-google 4u a_inode 0,16 0 58 [eventpoll:5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21]
dnsproxy 436873 dnsproxy-google 5u a_inode 0,16 0 58 [eventfd:5]
dnsproxy 436873 dnsproxy-google 6u IPv4 365616831 0t0 UDP 127.0.0.6:domain
dnsproxy 436873 dnsproxy-google 7u IPv4 365616836 0t0 TCP 127.0.0.6:domain (LISTEN)
dnsproxy 436873 dnsproxy-google 8u IPv6 365979239 0t0 UDP *:42047
dnsproxy 436873 dnsproxy-google 9u IPv6 366019813 0t0 UDP *:52678
dnsproxy 436873 dnsproxy-google 10u IPv6 365946353 0t0 UDP *:34188
dnsproxy 436873 dnsproxy-google 11u IPv6 365983107 0t0 UDP *:39381
dnsproxy 436873 dnsproxy-google 12u IPv6 366008373 0t0 UDP *:57130
dnsproxy 436873 dnsproxy-google 13u IPv6 366014604 0t0 UDP *:37532
dnsproxy 436873 dnsproxy-google 14u IPv6 366011470 0t0 UDP *:49196
dnsproxy 436873 dnsproxy-google 15u IPv6 366021273 0t0 UDP *:58625
dnsproxy 436873 dnsproxy-google 16u IPv6 366025846 0t0 UDP *:34846
dnsproxy 436873 dnsproxy-google 17u IPv6 366000931 0t0 UDP *:56331
dnsproxy 436873 dnsproxy-google 18u IPv6 365892103 0t0 UDP *:46402
dnsproxy 436873 dnsproxy-google 19u IPv6 366021275 0t0 UDP *:56870
dnsproxy 436873 dnsproxy-google 20u IPv6 365892105 0t0 UDP *:49549
dnsproxy 436873 dnsproxy-google 21u IPv6 365908932 0t0 UDP *:56892
```

Eventually, as further `0-RTT rejected` errors accumulate, all local ports are exhausted and DNS resolution begins to fail:
```
Jul 17 14:31:06 dnsproxy[423785]: 2026/07/17 14:31:06.739988 ERROR exchange failed prefix=dnsproxy upstream=https://dns.google:443/dns-query question=";5-prod-dynamite-prod-07-us-signaler-pa.clients6.google.com.\tIN\t A" duration=9.433834ms err="requesting https://dns.google:443/dns-query: Get_0rtt \"https://dns.google:443/dns-query?dns=AAABEAABAAAAAAABJjUtcHJvZC1keW5hbWl0ZS1wcm9kLTA3LXVzLXNpZ25hbGVyLXBhCGNsaWVudHM2Bmdvb2dsZQNjb20AAAEAAQAAKQTQAACAAAAA\": listen udp 0.0.0.0:0: bind: address already in use"
Jul 17 14:31:06 dnsproxy[423785]: 2026/07/17 14:31:06.740656 ERROR exchange failed prefix=dnsproxy upstream=https://dns.google:443/dns-query question=";5-prod-dynamite-prod-07-us-signaler-pa.clients6.google.com.\tIN\t HTTPS" duration=10.310516ms err="requesting https://dns.google:443/dns-query: Get_0rtt \"https://dns.google:443/dns-query?dns=AAABEAABAAAAAAABJjUtcHJvZC1keW5hbWl0ZS1wcm9kLTA3LXVzLXNpZ25hbGVyLXBhCGNsaWVudHM2Bmdvb2dsZQNjb20AAEEAAQAAKQTQAACAAAAA\": listen udp 0.0.0.0:0: bind: address already in use"
Jul 17 14:31:07 dnsproxy[423785]: 2026/07/17 14:31:07.267416 ERROR exchange failed prefix=dnsproxy upstream=https://dns.google:443/dns-query question=";storage.googleapis.com.\tIN\t A" duration=10.787386ms err="requesting https://dns.google:443/dns-query: Get_0rtt \"https://dns.google:443/dns-query?dns=AAABEAABAAAAAAABB3N0b3JhZ2UKZ29vZ2xlYXBpcwNjb20AAAEAAQAAKQTQAACAAAAA\": listen udp 0.0.0.0:0: bind: address already in use"
Jul 17 14:31:07 dnsproxy[423785]: 2026/07/17 14:31:07.324147 ERROR exchange failed prefix=dnsproxy upstream=https://dns.google:443/dns-query question=";prod-dynamite-prod-04-us-signaler-pa.clients6.google.com.\tIN\t HTTPS" duration=10.892828ms err="requesting https://dns.google:443/dns-query: Get_0rtt \"https://dns.google:443/dns-query?dns=AAABEAABAAAAAAABJHByb2QtZHluYW1pdGUtcHJvZC0wNC11cy1zaWduYWxlci1wYQhjbGllbnRzNgZnb29nbGUDY29tAABBAAEAACkE0AAAgAAAAA\": listen udp 0.0.0.0:0: bind: address already in use"
Jul 17 14:31:07 dnsproxy[423785]: 2026/07/17 14:31:07.325076 ERROR exchange failed prefix=dnsproxy upstream=https://dns.google:443/dns-query question=";prod-dynamite-prod-04-us-signaler-pa.clients6.google.com.\tIN\t A" duration=11.908636ms err="requesting https://dns.google:443/dns-query: Get_0rtt \"https://dns.google:443/dns-query?dns=AAABEAABAAAAAAABJHByb2QtZHluYW1pdGUtcHJvZC0wNC11cy1zaWduYWxlci1wYQhjbGllbnRzNgZnb29nbGUDY29tAAABAAEAACkE0AAAgAAAAA\": listen udp 0.0.0.0:0: bind: address already in use"
Jul 17 14:31:07 dnsproxy[423785]: 2026/07/17 14:31:07.359561 ERROR exchange failed prefix=dnsproxy upstream=https://dns.google:443/dns-query question=";prod-dynamite-prod-04-us-signaler-pa.clients6.google.com.\tIN\t A" duration=11.576853ms err="requesting https://dns.google:443/dns-query: Get_0rtt \"https://dns.google:443/dns-query?dns=AAABEAABAAAAAAABJHByb2QtZHluYW1pdGUtcHJvZC0wNC11cy1zaWduYWxlci1wYQhjbGllbnRzNgZnb29nbGUDY29tAAABAAEAACkE0AAAgAAAAA\": listen udp 0.0.0.0:0: bind: address already in use"
Jul 17 14:31:07 dnsproxy[423785]: 2026/07/17 14:31:07.376394 ERROR exchange failed prefix=dnsproxy upstream=https://dns.google:443/dns-query question=";ie_sla0.apple-dns.net.\tIN\t A" duration=11.355851ms err="requesting https://dns.google:443/dns-query: Get_0rtt \"https://dns.google:443/dns-query?dns=AAABEAABAAAAAAABB2llX3NsYTAJYXBwbGUtZG5zA25ldAAAAQABAAApBNAAAIAAAAA\": listen udp 0.0.0.0:0: bind: address already in use"
Jul 17 14:31:07 dnsproxy[423785]: 2026/07/17 14:31:07.377400 ERROR exchange failed prefix=dnsproxy upstream=https://dns.google:443/dns-query question=";prod-dynamite-prod-04-us-signaler-pa.clients6.google.com.\tIN\t A" duration=7.240127ms err="requesting https://dns.google:443/dns-query: Get_0rtt \"https://dns.google:443/dns-query?dns=AAABEAABAAAAAAABJHByb2QtZHluYW1pdGUtcHJvZC0wNC11cy1zaWduYWxlci1wYQhjbGllbnRzNgZnb29nbGUDY29tAAABAAEAACkE0AAAgAAAAA\": listen udp 0.0.0.0:0: bind: address already in use"
```