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fix: correct MCP stdio JSON-RPC framing and handshake #6

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Merged
dedsecorg merged 6 commits into from
Aug 28, 2026
Merged

fix: correct MCP stdio JSON-RPC framing and handshake #6

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2f3a317
fix: correct MCP stdio JSON-RPC framing and handshake
Aug 28, 2026
f6bb881
Merge branch 'main' into fix/mcp-stdio-jsonrpc-framing
dedsecorg Aug 28, 2026
49aba89
fix: handle MCP ping method with empty result
Aug 28, 2026
ad8e278
fix: preserve JSON-RPC id encoding for string request ids
Aug 28, 2026
598629a
refactor: drop redundant stderr redirection on MCP log calls
Aug 28, 2026
f8c6539
fix: negotiate MCP protocolVersion in initialize handshake
Aug 28, 2026
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35 changes: 18 additions & 17 deletions bin/agentic-dns
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devin-ai-integration[bot] marked this conversation as resolved.
Original file line number Diff line number Diff line change
Expand Up @@ -54,7 +54,7 @@ SERVICES=(
)

# ---- Helper functions ----
log() { echo "[$(date '+%H:%M:%S')] $*"; }
log() { echo "[$(date '+%H:%M:%S')] $*" >&2; }

@devin-ai-integration devin-ai-integration Bot Aug 28, 2026

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📝 Info: log() to stderr also affects the API server

Routing log to stderr also moves the API server's startup lines off stdout. Benign visibility change, worth noting since it affects a path beyond MCP.

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@dedsecorg dedsecorg Aug 28, 2026

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Acknowledged, and intentional. The API server logs going to stderr is the correct convention (stdout stays clean for protocol/data output, diagnostics go to stderr). No behavior change for the API server itself - only which stream the startup banner uses. Leaving as-is.


is_listening() {
local addr="$1" port="$2"
Expand Down Expand Up @@ -359,28 +359,29 @@ cmd_api() {

cmd_mcp() {
log "Starting agentic-dns MCP server (JSON-RPC over stdio)..."
log "Tools: dns_status, dns_query, dns_trace, dns_health, dns_routes, dns_add_route, dns_remove_route, dns_bypass, dns_pihole_log"
log "Tools: dns_status, dns_query, dns_trace, dns_health, dns_routes, dns_bypass, dns_pihole_log"

while IFS= read -r line || [ -n "$line" ]; do
[ -z "$line" ] && continue

local method req_id
method=$(echo "$line" | jq -r '.method // empty' 2>/dev/null)
req_id=$(echo "$line" | jq -r '.id // 1' 2>/dev/null)
req_id=$(echo "$line" | jq -c '.id // 1' 2>/dev/null)

case "$method" in
"initialize")
local proto
proto=$(echo "$line" | jq -c '.params.protocolVersion // "2024-11-05"' 2>/dev/null)
printf '{"jsonrpc":"2.0","id":%s,"result":{"protocolVersion":%s,"capabilities":{"tools":{}},"serverInfo":{"name":"agentic-dns","version":"1.0.0"}}}\n' "$req_id" "$proto"
Comment on lines +374 to +375

@devin-ai-integration devin-ai-integration Bot Aug 28, 2026

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📝 Info: protocolVersion echoed back without negotiation

The initialize handler echoes the client's requested protocolVersion back verbatim rather than replying with a version the server supports. The server thus claims to support any version string a client sends. Low impact for this tools-only server.

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;;
"notifications/initialized"|"notifications/"*)
;;
"ping")
# MCP liveness ping: respond with an empty result object.
printf '{"jsonrpc":"2.0","id":%s,"result":{}}\n' "$req_id"
;;
"tools/list")
cat << MCP_RESP
{"jsonrpc":"2.0","id":${req_id},"result":{"tools":[
{"name":"dns_status","description":"Show status of all DNS services"},
{"name":"dns_query","description":"Query a domain through the DNS chain","input":{"domain":"string"}},
{"name":"dns_trace","description":"Trace DNS path with packet capture","input":{"domain":"string"}},
{"name":"dns_health","description":"Check health of all DNS services"},
{"name":"dns_routes","description":"List current routing rules"},
{"name":"dns_pihole_log","description":"Show recent PiHole query log"},
{"name":"dns_bypass","description":"Bypass a failing DNS service","input":{"service":"string","backup":"string"}}
]}}
MCP_RESP
printf '{"jsonrpc":"2.0","id":%s,"result":{"tools":[{"name":"dns_status","description":"Show status of all DNS services","inputSchema":{"type":"object","properties":{},"required":[]}},{"name":"dns_query","description":"Query a domain through the DNS chain","inputSchema":{"type":"object","properties":{"domain":{"type":"string","description":"Domain name to resolve"}},"required":["domain"]}},{"name":"dns_trace","description":"Trace DNS path with packet capture","inputSchema":{"type":"object","properties":{"domain":{"type":"string","description":"Domain name to trace"}},"required":["domain"]}},{"name":"dns_health","description":"Check health of all DNS services","inputSchema":{"type":"object","properties":{},"required":[]}},{"name":"dns_routes","description":"List current routing rules","inputSchema":{"type":"object","properties":{},"required":[]}},{"name":"dns_pihole_log","description":"Show recent PiHole query log","inputSchema":{"type":"object","properties":{},"required":[]}},{"name":"dns_bypass","description":"Bypass a failing DNS service","inputSchema":{"type":"object","properties":{"service":{"type":"string","description":"Service to bypass"},"backup":{"type":"string","description":"Backup service to use"}},"required":["service"]}}]}}\n' "$req_id"
;;
"tools/call")
local tool domain service backup
Expand All @@ -396,9 +397,9 @@ MCP_RESP
echo "{\"jsonrpc\":\"2.0\",\"id\":${req_id},\"result\":{\"content\":[{\"type\":\"text\",\"text\":$(echo "$out" | jq -Rs .)}]}}"
;;
"dns_query")
local result
result=$(dns_query "$domain")
echo "{\"jsonrpc\":\"2.0\",\"id\":${req_id},\"result\":{\"content\":[{\"type\":\"text\",\"text\":\"${result}\"}]}}"
local out
out=$(dns_query "$domain" 2>&1)
echo "{\"jsonrpc\":\"2.0\",\"id\":${req_id},\"result\":{\"content\":[{\"type\":\"text\",\"text\":$(echo "$out" | jq -Rs .)}]}}"
;;
"dns_trace")
local out
Expand Down
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