https://chatgpt.com/share/66f0680a-da5c-800e-ae65-832b4929778b
You said: I'm having an issue on this network, in my rhel7 terminal, where a certain name resolves with host and dig, but not with curl nor in python with socket.getaddrinfo. This likely comes down to a subtle difference in the use of the underlying system calls and a detail of the network connection. Let's troubleshoot it step-by-step using tools like strace, gdb, and custom test binaries written in C. I'm confused and taxed around issues like this. Speak really concisely and give clear concise examples or steps. ChatGPT said: ChatGPT Memory updated Let's break this down. First, we’ll start with strace to compare system calls. Trace curl: bash Copy code strace -o curl_trace.txt curl http://example.com Trace host: bash Copy code strace -o host_trace.txt host example.com Compare system calls: Look for differences in how they resolve names. Search for getaddrinfo or related calls: bash Copy code grep getaddrinfo curl_trace.txt host_trace.txt Next, if there's a difference, we can write a C test binary to inspect further. Would you like an example C snippet? 4o You said: I'm looking at curl_trace.txt and it looks like the syscalls disappear behind a call to clone. Could you update both command lines? Also, the failing url is https://stonkson.xyz (it's an arweave gateway that was speedy yesterday), and yes let's see an example C snippet. ChatGPT said: ChatGPT Memory updated To capture syscalls before and after the clone call, we’ll trace across forks: Updated curl trace: bash Copy code strace -ff -o curl_trace curl https://stonkson.xyz Updated host trace: bash Copy code strace -ff -o host_trace host stonkson.xyz This will output multiple files, one per process. Check the main trace files first, then forked traces (curl_trace.<PID>). Here’s an example C snippet to test getaddrinfo: c Copy code #include <stdio.h> #include <stdlib.h> #include <string.h> #include <netdb.h> int main() { struct addrinfo hints, *res; int err; memset(&hints, 0, sizeof(hints)); hints.ai_family = AF_UNSPEC; // IPv4 or IPv6 hints.ai_socktype = SOCK_STREAM; err = getaddrinfo("stonkson.xyz", "80", &hints, &res); if (err != 0) { fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(err)); return 1; } printf("Success: %s\n", "stonkson.xyz"); freeaddrinfo(res); return 0; } Compile with: bash Copy code gcc -o test_resolve test_resolve.c ./test_resolve This will test if getaddrinfo works directly in C. Let me know how it goes! 4o You said: thanks for those! I tried running test_resolve and it outputs getaddrinfo: Name or service not known, so we've found the failing codepath :/ . Maybe host performs the resolve manually, I'm still looking at the straces. ChatGPT said: ChatGPT You're welcome! The fact that getaddrinfo fails confirms the issue is related to system-level name resolution. You're right—host might be bypassing standard resolution and querying DNS manually using different syscalls. While reviewing straces, focus on: DNS lookups in host using sendto/recvfrom or connect on UDP port 53. curl and getaddrinfo traces likely failing on connect or returning an error code (check for EAI_*). Let me know if something stands out in the strace, and we can dig further. 4o You said: is there an easy way to know which strace outfile is the parent vs child process? ChatGPT said: ChatGPT Yes! You can easily identify the parent process in strace output by checking the file naming and content. File naming: The parent process trace will not have a PID suffix, e.g., curl_trace. Forked/child processes will have a .<PID> suffix, e.g., curl_trace.<PID>. Content: In each file, look for the clone or fork syscall. The parent process will have the clone/fork call, while the child will not. You can use grep to locate it: bash Copy code grep clone curl_trace grep clone curl_trace.<PID> The file where clone is called without any PID in its name is the parent. 4o You said: they all have a PID suffix, maybe my strace binary is different ChatGPT said: ChatGPT It sounds like your version of strace generates output files with PIDs for all processes, including the parent. To identify the parent process, try this: Check for the lowest PID: Typically, the parent process has the lowest PID among the trace files. List the files sorted by name: bash Copy code ls -1 curl_trace.* | sort Look for forks/clones: The parent process will be the one that calls clone or fork, indicating it's spawning child processes: bash Copy code grep clone curl_trace.* | grep -v "No such" The file with the clone/fork line is the parent. Let me know if this helps! 4o You said: what do you think /etc/host.conf and /lib64/libnss_mdns4_minimal.so.2 are? ChatGPT said: ChatGPT Here's a quick breakdown: /etc/host.conf: This file configures name resolution order and behavior for the libc resolver. It defines how the system looks up hostnames (e.g., hosts, DNS). Common directives include: order hosts,bind: Use /etc/hosts first, then DNS. multi on: Allows multiple IPs per hostname. It controls the system’s approach to resolving names, particularly with the getaddrinfo function. /lib64/libnss_mdns4_minimal.so.2: This library is part of the Name Service Switch (NSS), specifically for resolving names using multicast DNS (mDNS). It handles .local domains (e.g., hostname.local) commonly used for LAN discovery. If this is involved in your name resolution stack (via /etc/nsswitch.conf), it might attempt to resolve names using mDNS before standard DNS. Checking these files could reveal misconfigurations impacting your DNS lookups. Let me know if you'd like to inspect them further! 4o You said: it's also opening /lib64/libnss_dns.so.2 ChatGPT said: ChatGPT /lib64/libnss_dns.so.2 is part of the Name Service Switch (NSS) and is responsible for handling DNS lookups when specified in /etc/nsswitch.conf. This library is used by system functions like getaddrinfo to query DNS servers. In /etc/nsswitch.conf, you’ll likely find a line like this: makefile Copy code hosts: files dns This line means the system checks /etc/hosts first (via libnss_files.so.2), then DNS (via libnss_dns.so.2). If libnss_dns.so.2 is loaded, it indicates the system is attempting a DNS lookup. If there's an issue, it could stem from this library or how DNS is configured. You could review /etc/nsswitch.conf to see if something unusual is affecting the resolution order. 4o You said: i'm looking in the (failing) curl strace and i see it connecting directly to the nameserver (8.8.8.8) ChatGPT said: ChatGPT If curl is directly connecting to the nameserver (e.g., 8.8.8.8), that suggests it's bypassing typical system name resolution libraries (like libnss_dns.so.2) and performing its own DNS lookup using the configured nameserver. Things to check: DNS settings: Verify if curl is using a different DNS resolver configuration from your system, possibly specified in /etc/resolv.conf. Look for entries like: bash Copy code cat /etc/resolv.conf Firewall or network issues: If curl is trying to reach 8.8.8.8 but failing, there could be a network problem or DNS resolution timeout specific to this connection. Ensure the DNS request is reaching the server. Compare with host: The host command might be successfully resolving because it's using a different method (like system libraries or a specific DNS server). If curl connects but still fails to resolve, the issue may lie deeper in its request flow or network path to 8.8.8.8. 4o You said: Here's the strace snippet of the first lookup, I think. Is there enough information here to precisely decode what is happening, or do I need to run a new strace to include more? connect(7, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("8.8.8.8")}, 16) = 0 poll([{fd=7, events=POLLOUT}], 1, 0) = 1 ([{fd=7, revents=POLLOUT}]) sendmmsg(7, [{msg_hdr={msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="\30\25\1\0\0\1\0\0\0\0\0\0\10stonkson\3xyz\0\0\1\0\1", iov_len=30}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, msg_len=30}, {msg_hdr={msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="\211+\1\0\0\1\0\0\0\0\0\0\10stonkson\3xyz\0\0\34\0\1", iov_len=30}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, msg_len=30}], 2, MSG_NOSIGNAL) = 2 poll([{fd=7, events=POLLIN}], 1, 5000) = 1 ([{fd=7, revents=POLLIN}]) ioctl(7, FIONREAD, [73]) = 0 recvfrom(7, "\30\25\201\200\0\1\0\1\0\0\0\0\10stonkson\3xyz\0\0\1\0\1\300\f"..., 2048, 0, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("8.8.8.8")}, [28->16]) = 73 poll([{fd=7, events=POLLIN}], 1, 4962) = 0 (Timeout) poll([{fd=7, events=POLLOUT}], 1, 0) = 1 ([{fd=7, revents=POLLOUT}]) sendto(7, "\30\25\1\0\0\1\0\0\0\0\0\0\10stonkson\3xyz\0\0\1\0\1", 30, MSG_NOSIGNAL, NULL, 0) = 30 poll([{fd=7, events=POLLIN}], 1, 5000) = 0 (Timeout) ChatGPT said: ChatGPT The strace snippet provides enough information to analyze what's happening in the DNS lookup process. Here’s a breakdown: connect(7, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("8.8.8.8")}, 16) = 0: curl connects to Google's DNS server (8.8.8.8) on port 53 (DNS). The connection is successful (= 0). sendmmsg(7, ...) = 2: curl sends two DNS queries using the sendmmsg system call, which can send multiple messages. The two queries are: One for the A record (IPv4 address) of stonkson.xyz (\10stonkson\3xyz\0\0\1\0\1 where \0\1 is the type A query). One for an AAAA record (IPv6 address) (\10stonkson\3xyz\0\0\34\0\1 where \0\34 is the type AAAA query). recvfrom(7, ...) = 73: The DNS server (8.8.8.8) replies, and curl successfully receives 73 bytes, containing the response to the A record query (stonkson.xyz A record). However, this is where things likely start to break down. Timeouts: After receiving the first response, curl appears to wait for additional data (possibly the AAAA response), but the subsequent polls on the socket time out (poll([{fd=7, events=POLLIN}], 1, 4962) = 0 (Timeout)). The trace indicates that curl successfully sent DNS queries and got a response for the A record but encountered timeouts for subsequent queries, likely affecting resolution completion. Next Steps: mDNS/AAAA records: Since it times out after sending multiple queries, try restricting curl to IPv4 only by adding -4: bash Copy code curl -4 https://stonkson.xyz Check DNS settings: Look at /etc/resolv.conf to ensure it’s configured correctly (e.g., no unreachable nameservers). Would you like to dive further into DNS server behavior, or is there another path you want to explore? 4o You said: this is awesome! maybe this network is filtering ipv6 name resolution packets! we might have figured it out! we at least made a huge step :D ChatGPT said: ChatGPT That's fantastic! 🎉 If the network is filtering IPv6 name resolution packets, it would explain the timeouts you're seeing. For now, restricting curl to IPv4 using -4 is a solid workaround. You've definitely made a huge step! If you want to further confirm the IPv6 filtering theory, you can: Test with dig for AAAA: bash Copy code dig AAAA stonkson.xyz See if it times out or if there's no response. Test IPv6 connectivity: You can also try: bash Copy code ping6 google.com Feel free to let me know if more troubleshooting comes up or if you need to dive deeper! 4o You said: this is probably a bug in curl that nobody thought of because what a weird firewall behavior ChatGPT said: ChatGPT It does sound like an unusual case! If the network filters IPv6 DNS responses while allowing the queries, it could catch many applications off guard, including curl. If you suspect a bug or unexpected behavior in curl, consider: Reporting it: You could report this behavior on the curl GitHub issues page, especially if you can reproduce it consistently. Workaround: Using the -4 option is a good immediate workaround until the behavior is understood better or fixed. You might not be alone in experiencing this—other users may encounter similar issues in similar network environments. If you have more insights or further questions, I'm here to help! 4o mini You said: noooooo curl -4 doesn't work :/ ChatGPT said: ChatGPT Sorry to hear that! If curl -4 still doesn’t work, it suggests the issue might be deeper than just IPv6 filtering. Here are a few things to check: DNS Configuration: Double-check /etc/resolv.conf to ensure it only points to IPv4 DNS servers. Firewall Rules: If you have local firewall rules (e.g., iptables), check if they might be blocking outbound DNS requests. Alternative Tools: Try using wget or http command-line tools with the same URL to see if they behave differently. Verbose Output: Run curl with the -v flag to get more insight into what's happening: bash Copy code curl -4 -v https://stonkson.xyz Let me know what you find! 4o mini You said: additionally dig AAAA succeeds ChatGPT said: ChatGPT If dig AAAA stonkson.xyz succeeds but curl -4 still fails, it suggests that the DNS resolution is working correctly but that curl might still have trouble connecting. Here are some next steps: Check Ports: Ensure that port 443 (for HTTPS) is open and reachable. You can test this using telnet or nc: bash Copy code telnet stonkson.xyz 443 or bash Copy code nc -zv stonkson.xyz 443 Test with a Different URL: Try curl with a different, known working URL to see if the issue is specific to stonkson.xyz. Use curl with IP: Try directly using the resolved IPv4 address with curl: bash Copy code curl http://<resolved_ip> Check curl Version: Ensure you are using the latest version of curl, as bugs can be fixed in newer releases. Let me know what you discover! 4o mini You said: wget also fails ChatGPT said: ChatGPT If both curl and wget fail, it indicates a more systemic issue rather than a bug in curl. Here are some things to investigate further: Network Connectivity: Check if you can reach other sites. Try: bash Copy code ping stonkson.xyz ping google.com DNS Server: Confirm that the DNS server you're using (e.g., 8.8.8.8) is responsive: bash Copy code dig @8.8.8.8 stonkson.xyz Check Default Gateway: Ensure your default gateway is set correctly: bash Copy code ip route Firewall: Look at local firewall settings (like iptables) to see if something is blocking outbound traffic. Check Routing: Use traceroute to see if packets are being blocked: bash Copy code traceroute stonkson.xyz This should help narrow down where the issue lies. Let me know what you find! 4o mini You said: a lot of your advice isn't right in my opinion, although you don't have complete information since you're only acting on this chat window. let's run another strace on curl -4. is there a way to prevent it from eliding long passed buffers so everything is included in the dump? ChatGPT said: ChatGPT Memory updated To prevent strace from eliding long passed buffers and ensure everything is included, you can use the -s option to specify the maximum string size to print. Set it to a larger value, like 1024 or even 4096, to capture more data: bash Copy code strace -s 4096 -o curl_trace.txt curl -4 https://stonkson.xyz This will allow you to see more of the buffers involved in the system calls. Let me know what you find in the new output! 4o mini You said: It looks like the failing strace's use connect and sendmmsg and the succeeding ones use bind and sendmsg. Can we figure out what API is being used when it does bind? Is the right approach to set a breakpoint on a syscall and look at the backtrace or is there a better way? ChatGPT said: ChatGPT You're on the right track! Setting a breakpoint on the syscall and examining the backtrace is a good way to figure out which API function is responsible for bind and sendmsg. Here's how you can approach this step-by-step: 1. Using gdb to set breakpoints on syscalls: You can attach gdb to a running instance of curl and set breakpoints on the bind and sendmsg syscalls. When the breakpoint is hit, you'll be able to look at the backtrace to find the calling API function. For example: bash Copy code gdb --args curl -4 https://stonkson.xyz Then in gdb, set breakpoints on the syscalls and run the program: gdb Copy code b bind b sendmsg run Once the breakpoint is hit, use bt to get the backtrace: gdb Copy code bt This will show you the chain of function calls leading to the syscall, helping you figure out the higher-level API responsible. 2. Alternatively, using strace with specific filtering: If you want to see how curl reaches these syscalls without diving into gdb, you can trace just the relevant syscalls with strace: bash Copy code strace -e trace=bind,sendmsg,sendmmsg -s 4096 -o curl_trace.txt curl -4 https://stonkson.xyz This will focus on those specific syscalls, making it easier to pinpoint differences. 3. Investigating the differences: bind + sendmsg: This suggests that the application is explicitly binding to a local socket before sending data, which is typical in a manual DNS query implementation. connect + sendmmsg: This suggests that curl is using a more traditional client-side socket approach, where it connects to a DNS server and sends multiple messages in one go. By examining the backtrace from gdb, you'll get a clearer picture of which APIs are leading to the use of bind in successful cases and connect in failing ones. Would you like more guidance on using gdb or analyzing the results from the strace? 4o You said: You recommend strace here, but I don't know how I'd find the API used with strace as it only debugs syscalls usually? I ran gdb on host rather than curl because host succeeds and also uses bind. It looks like it's passing through a libisc. What is libisc? (gdb) bt #0 0x00007ffff4d277f0 in bind () from /lib64/libc.so.6 #1 0x00007ffff71225e6 in cmsgsend.isra () from /lib64/libisc.so.169 #2 0x00007ffff7122acd in try_dscp () from /lib64/libisc.so.169 #3 0x00007ffff5cb620b in __pthread_once_slow () from /lib64/libpthread.so.0 #4 0x00007ffff7123177 in isc_net_probedscp () from /lib64/libisc.so.169 #5 0x00007ffff712a128 in socket_create () from /lib64/libisc.so.169 #6 0x00000000004112c5 in send_udp () #7 0x000000000040fb45 in start_lookup () #8 0x0000000000411c26 in onrun_callback () #9 0x00007ffff7112deb in run () from /lib64/libisc.so.169 #10 0x00007ffff5cb7ea5 in start_thread () from /lib64/libpthread.so.0 #11 0x00007ffff4d26b0d in clone () from /lib64/libc.so.6 ChatGPT said: ChatGPT Memory updated libisc is part of the ISC (Internet Systems Consortium) libraries, which are used primarily by BIND (Berkeley Internet Name Domain), a widely used DNS server software. The library provides low-level network and system interaction utilities for handling tasks like DNS queries, socket management, and protocol handling. In the context of your gdb trace, libisc.so is likely responsible for managing the DNS query process that host performs, including creating and managing sockets, sending UDP packets, and processing responses. Key Functions from the Stack Trace: isc_net_probedscp: This function likely probes network conditions, possibly related to socket settings or QoS. socket_create: This function handles creating the socket for DNS queries. send_udp: This function sends the DNS query over UDP, which is typical for DNS resolution. Why This Matters: host appears to use the libisc library, which implements more fine-grained socket handling (e.g., manually binding to a local interface). This could explain why host succeeds while curl doesn't, as curl likely uses more generic system libraries for DNS resolution (e.g., libc). Next Steps: Compare APIs: It might be worth comparing how curl handles DNS queries versus host using libisc. Since libisc is part of BIND's suite, it might handle things like retries, binding, and packet-level adjustments more robustly. Inspect libcurl: You could try investigating if curl has support for using alternate DNS libraries like libisc (though it typically uses libc). Would you like to explore switching curl’s resolver or dig deeper into libisc functions? 4o You said: what are the functions in the backtrace that don't have a shared library trailing them? are they part of the host binary? ChatGPT said: ChatGPT Yes, the functions in the backtrace that don't have a shared library trailing them (such as send_udp, start_lookup, and onrun_callback) are most likely part of the host binary itself. These functions are implemented directly in the host executable or in code linked into the host binary during compilation. In your backtrace: send_udp: This function seems to handle sending DNS queries over UDP, as part of the core logic of host. start_lookup: Likely the function that kicks off the DNS resolution process. onrun_callback: This is probably a callback function used to manage asynchronous events during DNS resolution. These functions work together with the ISC libraries (libisc) and other system libraries (libc, libpthread) to perform the actual DNS query. So yes, these are part of the host program itself, not external libraries. You could explore the source code of host (part of the BIND utilities) to see the exact implementations if needed. Let me know if you'd like further clarification! 4o You said: Do you know offhand what the host source code might look like, to write an example start_lookup function, maybe exchange parts you don't know confidently with '...'? I have host 9.11.4-P2-RedHat-9.11.4-26.P2.el7_9.13 . ChatGPT said: ChatGPT Certainly! The host command is part of the BIND suite, and its source code can be found within ISC BIND’s utilities, specifically in the DNS query handling code. Based on the version you provided, 9.11.4-P2 is a part of the BIND 9 release, which is quite stable and widely used. Here's a general approximation of what the start_lookup function might look like based on typical DNS resolution workflows in BIND, with placeholders where exact details may differ: c Copy code #include <isc/result.h> #include <isc/mem.h> #include <isc/task.h> #include <isc/socket.h> #include <isc/event.h> #include <dns/message.h> #include <dns/name.h> void start_lookup(dns_name_t *name, isc_task_t *task) { // 1. Set up memory context and task for async operation isc_mem_t *mctx; isc_socket_t *sock; dns_message_t *query_msg; isc_result_t result; // Initialize memory context (this is crucial for managing resources) result = isc_mem_create(0, 0, &mctx); if (result != ISC_R_SUCCESS) { fprintf(stderr, "Memory context creation failed.\n"); return; } // 2. Prepare the DNS query message result = dns_message_create(mctx, DNS_MESSAGE_INTENTRENDER, &query_msg); if (result != ISC_R_SUCCESS) { fprintf(stderr, "Failed to create DNS query message.\n"); isc_mem_destroy(&mctx); return; } // 3. Add the question section to the query (ask for an A record, for example) dns_question_t *question; dns_name_init(name, NULL); // Init DNS name object dns_name_fromstring(name, "example.com.", 0, NULL); // Set the domain dns_question_create(mctx, name, dns_rdatatype_a, dns_rdataclass_in, &question); dns_message_addquestion(query_msg, question); // 4. Create a socket (UDP in most cases for DNS queries) result = isc_socket_create(mctx, AF_INET, isc_sockettype_udp, &sock); if (result != ISC_R_SUCCESS) { fprintf(stderr, "Socket creation failed.\n"); dns_message_destroy(&query_msg); isc_mem_destroy(&mctx); return; } // 5. Set up callback/event handlers isc_task_onrun(task, onrun_callback, query_msg); // 6. Send the query (this is part of the host binary and sends the packet) send_udp(sock, query_msg); // 7. Clean up would follow after async result is received } // Example callback for when the task is run (after the query is sent) void onrun_callback(isc_task_t *task, isc_event_t *event) { // Process the response or handle errors printf("DNS lookup completed!\n"); // Clean up here } Key Components: isc_mem_create: Creates a memory context to manage memory allocations. dns_message_create: Initializes a DNS query message. dns_question_create: Prepares the DNS query (for example, asking for an A record). isc_socket_create: Sets up a UDP socket to send the query. send_udp: Sends the query message using the previously created socket. onrun_callback: Handles the response when it's received. This is a very simplified outline of what the start_lookup function might look like in the context of BIND’s DNS resolution. The actual code could have more steps, especially around memory management, socket options, and handling different types of queries or retries. You can find the full source code for the BIND suite, including host, in the BIND repository: https://gitlab.isc.org/isc-projects/bind9. The source code for host is typically located in the bin/dig directory of the BIND utilities. Let me know if you need more details or would like to explore something else! 4o You said: Is dig from BIND too? ChatGPT said: ChatGPT Yes, dig (Domain Information Groper) is also part of the BIND suite, just like host. It uses many of the same libraries as host, such as libisc (Internet Systems Consortium library) and libdns. Both dig and host share core DNS resolution logic, but dig provides more detailed output and diagnostic capabilities, while host offers a simpler interface for querying DNS records. In terms of source code structure, dig and host are often grouped together because they rely on similar backend functions. Both tools are included in the BIND 9 utilities. You can find the source for dig under the same BIND repository, typically in the bin/dig directory. This directory contains the core logic for both dig and host. So, yes, dig is part of BIND, and it shares much of the same infrastructure and libraries as host. 4o You said: it sounds like libisc is working on my system but libc might not be. Can you write a concise test that might succeed in looking up the name on my system, given what we've gone over? ChatGPT said: ChatGPT Given that libisc works on your system (as used by host and dig), but libc-based lookups (getaddrinfo in curl or Python) are failing, you can test DNS resolution using libisc directly in C. Here’s a concise test that leverages libisc to perform a DNS lookup: c Copy code #include <stdio.h> #include <isc/result.h> #include <isc/mem.h> #include <isc/socket.h> #include <isc/task.h> #include <dns/message.h> #include <dns/name.h> #include <dns/rdataclass.h> #include <dns/rdataset.h> #include <dns/dispatch.h> void lookup(const char *hostname) { isc_mem_t *mctx; dns_message_t *query_msg; dns_name_t dnsname; isc_result_t result; // Initialize memory context result = isc_mem_create(0, 0, &mctx); if (result != ISC_R_SUCCESS) { fprintf(stderr, "Memory context creation failed.\n"); return; } // Create DNS message result = dns_message_create(mctx, DNS_MESSAGE_INTENTRENDER, &query_msg); if (result != ISC_R_SUCCESS) { fprintf(stderr, "Failed to create DNS query message.\n"); isc_mem_destroy(&mctx); return; } // Initialize DNS name dns_name_init(&dnsname, NULL); result = dns_name_fromstring(&dnsname, hostname, 0, NULL); if (result != ISC_R_SUCCESS) { fprintf(stderr, "Invalid DNS name: %s\n", hostname); dns_message_destroy(&query_msg); isc_mem_destroy(&mctx); return; } // Set up the question (A record, IN class) dns_question_t *question; dns_question_create(mctx, &dnsname, dns_rdatatype_a, dns_rdataclass_in, &question); dns_message_addquestion(query_msg, question); // (In a full implementation, you'd now send this query over UDP using isc_socket and process the response) printf("DNS query for %s prepared successfully (using libisc).\n", hostname); // Clean up dns_message_destroy(&query_msg); isc_mem_destroy(&mctx); } int main() { const char *hostname = "stonkson.xyz"; lookup(hostname); return 0; } Key Parts of the Test: isc_mem_create: Initializes the memory context required for libisc operations. dns_message_create: Prepares a DNS query message. dns_name_fromstring: Converts the hostname into a dns_name_t object for query purposes. dns_question_create: Prepares a DNS question for an A record lookup. Socket Operations (not shown): In a full implementation, you'd use isc_socket to send this query and receive a response, similar to what host does. Compilation: You'll need to link against ISC and DNS libraries: bash Copy code gcc -o test_isc test_isc.c -ldns -lisc This example prepares the DNS query using libisc as host does. If you need help extending it further to handle socket operations and responses, let me know! 4o You said: i dont' have <isc/result.h> i'm like missing a devel package on this rhel7 system, do you know which one? ChatGPT said: ChatGPT On RHEL 7, the development headers for BIND libraries, including libisc, are provided by the bind-devel package. To get access to <isc/result.h> and other ISC-related headers, you can install this package using: bash Copy code sudo yum install bind-devel This should provide the necessary headers and libraries for compiling and linking code that uses libisc and other BIND components. After installing bind-devel, try compiling the program again. 4o You said: I'm going to have to go after this, but it would have been cool if we had somehow gone faster, to next look into libc and see what the problem is, and maybe backport a fix to my old libc. ChatGPT said: ChatGPT Memory updated I understand—it would have been great to dive into the libc issues and explore potential fixes! If you return and want to continue troubleshooting or backporting a fix for libc, we can definitely take that on step by step. Feel free to reach out when you're ready, and good luck with your next steps! 4o
