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https://github.com/coredns/coredns.git
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First commit
This commit is contained in:
Miek Gieben
379
core/parse/parsing.go
Normal file
379
core/parse/parsing.go
Normal file
@@ -0,0 +1,379 @@
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package parse
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import (
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"net"
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"os"
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"path/filepath"
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"strings"
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"github.com/miekg/dns"
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)
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type parser struct {
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Dispenser
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block ServerBlock // current server block being parsed
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eof bool // if we encounter a valid EOF in a hard place
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checkDirectives bool // if true, directives must be known
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}
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func (p *parser) parseAll() ([]ServerBlock, error) {
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var blocks []ServerBlock
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for p.Next() {
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err := p.parseOne()
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if err != nil {
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return blocks, err
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}
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if len(p.block.Addresses) > 0 {
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blocks = append(blocks, p.block)
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}
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}
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return blocks, nil
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}
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func (p *parser) parseOne() error {
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p.block = ServerBlock{Tokens: make(map[string][]token)}
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err := p.begin()
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if err != nil {
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return err
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}
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return nil
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}
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func (p *parser) begin() error {
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if len(p.tokens) == 0 {
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return nil
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}
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err := p.addresses()
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if err != nil {
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return err
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}
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if p.eof {
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// this happens if the Caddyfile consists of only
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// a line of addresses and nothing else
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return nil
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}
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err = p.blockContents()
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if err != nil {
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return err
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}
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return nil
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}
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func (p *parser) addresses() error {
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var expectingAnother bool
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for {
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tkn := replaceEnvVars(p.Val())
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// special case: import directive replaces tokens during parse-time
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if tkn == "import" && p.isNewLine() {
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err := p.doImport()
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if err != nil {
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return err
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}
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continue
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}
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// Open brace definitely indicates end of addresses
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if tkn == "{" {
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if expectingAnother {
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return p.Errf("Expected another address but had '%s' - check for extra comma", tkn)
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}
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break
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}
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if tkn != "" { // empty token possible if user typed "" in Caddyfile
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// Trailing comma indicates another address will follow, which
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// may possibly be on the next line
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if tkn[len(tkn)-1] == ',' {
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tkn = tkn[:len(tkn)-1]
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expectingAnother = true
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} else {
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expectingAnother = false // but we may still see another one on this line
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}
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// Parse and save this address
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addr, err := standardAddress(tkn)
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if err != nil {
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return err
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}
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p.block.Addresses = append(p.block.Addresses, addr)
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}
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// Advance token and possibly break out of loop or return error
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hasNext := p.Next()
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if expectingAnother && !hasNext {
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return p.EOFErr()
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}
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if !hasNext {
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p.eof = true
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break // EOF
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}
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if !expectingAnother && p.isNewLine() {
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break
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}
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}
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return nil
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}
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func (p *parser) blockContents() error {
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errOpenCurlyBrace := p.openCurlyBrace()
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if errOpenCurlyBrace != nil {
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// single-server configs don't need curly braces
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p.cursor--
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}
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err := p.directives()
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if err != nil {
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return err
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}
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// Only look for close curly brace if there was an opening
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if errOpenCurlyBrace == nil {
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err = p.closeCurlyBrace()
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if err != nil {
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return err
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}
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}
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return nil
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}
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// directives parses through all the lines for directives
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// and it expects the next token to be the first
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// directive. It goes until EOF or closing curly brace
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// which ends the server block.
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func (p *parser) directives() error {
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for p.Next() {
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// end of server block
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if p.Val() == "}" {
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break
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}
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// special case: import directive replaces tokens during parse-time
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if p.Val() == "import" {
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err := p.doImport()
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if err != nil {
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return err
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}
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p.cursor-- // cursor is advanced when we continue, so roll back one more
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continue
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}
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// normal case: parse a directive on this line
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if err := p.directive(); err != nil {
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return err
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}
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}
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return nil
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}
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// doImport swaps out the import directive and its argument
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// (a total of 2 tokens) with the tokens in the specified file
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// or globbing pattern. When the function returns, the cursor
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// is on the token before where the import directive was. In
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// other words, call Next() to access the first token that was
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// imported.
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func (p *parser) doImport() error {
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// syntax check
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if !p.NextArg() {
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return p.ArgErr()
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}
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importPattern := p.Val()
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if p.NextArg() {
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return p.Err("Import takes only one argument (glob pattern or file)")
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}
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// do glob
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matches, err := filepath.Glob(importPattern)
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if err != nil {
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return p.Errf("Failed to use import pattern %s: %v", importPattern, err)
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}
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if len(matches) == 0 {
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return p.Errf("No files matching import pattern %s", importPattern)
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}
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// splice out the import directive and its argument (2 tokens total)
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tokensBefore := p.tokens[:p.cursor-1]
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tokensAfter := p.tokens[p.cursor+1:]
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// collect all the imported tokens
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var importedTokens []token
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for _, importFile := range matches {
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newTokens, err := p.doSingleImport(importFile)
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if err != nil {
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return err
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}
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importedTokens = append(importedTokens, newTokens...)
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}
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// splice the imported tokens in the place of the import statement
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// and rewind cursor so Next() will land on first imported token
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p.tokens = append(tokensBefore, append(importedTokens, tokensAfter...)...)
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p.cursor--
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return nil
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}
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// doSingleImport lexes the individual file at importFile and returns
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// its tokens or an error, if any.
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func (p *parser) doSingleImport(importFile string) ([]token, error) {
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file, err := os.Open(importFile)
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if err != nil {
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return nil, p.Errf("Could not import %s: %v", importFile, err)
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}
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defer file.Close()
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importedTokens := allTokens(file)
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// Tack the filename onto these tokens so errors show the imported file's name
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filename := filepath.Base(importFile)
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for i := 0; i < len(importedTokens); i++ {
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importedTokens[i].file = filename
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}
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return importedTokens, nil
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}
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// directive collects tokens until the directive's scope
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// closes (either end of line or end of curly brace block).
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// It expects the currently-loaded token to be a directive
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// (or } that ends a server block). The collected tokens
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// are loaded into the current server block for later use
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// by directive setup functions.
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func (p *parser) directive() error {
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dir := p.Val()
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nesting := 0
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if p.checkDirectives {
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if _, ok := ValidDirectives[dir]; !ok {
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return p.Errf("Unknown directive '%s'", dir)
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}
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}
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// The directive itself is appended as a relevant token
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p.block.Tokens[dir] = append(p.block.Tokens[dir], p.tokens[p.cursor])
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for p.Next() {
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if p.Val() == "{" {
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nesting++
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} else if p.isNewLine() && nesting == 0 {
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p.cursor-- // read too far
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break
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} else if p.Val() == "}" && nesting > 0 {
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nesting--
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} else if p.Val() == "}" && nesting == 0 {
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return p.Err("Unexpected '}' because no matching opening brace")
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}
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p.tokens[p.cursor].text = replaceEnvVars(p.tokens[p.cursor].text)
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p.block.Tokens[dir] = append(p.block.Tokens[dir], p.tokens[p.cursor])
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}
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if nesting > 0 {
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return p.EOFErr()
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}
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return nil
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}
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// openCurlyBrace expects the current token to be an
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// opening curly brace. This acts like an assertion
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// because it returns an error if the token is not
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// a opening curly brace. It does NOT advance the token.
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func (p *parser) openCurlyBrace() error {
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if p.Val() != "{" {
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return p.SyntaxErr("{")
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}
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return nil
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}
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// closeCurlyBrace expects the current token to be
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// a closing curly brace. This acts like an assertion
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// because it returns an error if the token is not
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// a closing curly brace. It does NOT advance the token.
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func (p *parser) closeCurlyBrace() error {
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if p.Val() != "}" {
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return p.SyntaxErr("}")
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}
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return nil
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}
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// standardAddress parses an address string into a structured format with separate
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// host, and port portions, as well as the original input string.
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func standardAddress(str string) (address, error) {
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var err error
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// first check for scheme and strip it off
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input := str
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// separate host and port
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host, port, err := net.SplitHostPort(str)
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if err != nil {
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host, port, err = net.SplitHostPort(str + ":")
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// no error check here; return err at end of function
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}
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// see if we can set port based off scheme
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if port == "" {
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port = "53"
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}
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return address{Original: input, Host: strings.ToLower(dns.Fqdn(host)), Port: port}, err
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}
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// replaceEnvVars replaces environment variables that appear in the token
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// and understands both the $UNIX and %WINDOWS% syntaxes.
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func replaceEnvVars(s string) string {
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s = replaceEnvReferences(s, "{%", "%}")
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s = replaceEnvReferences(s, "{$", "}")
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return s
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}
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// replaceEnvReferences performs the actual replacement of env variables
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// in s, given the placeholder start and placeholder end strings.
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func replaceEnvReferences(s, refStart, refEnd string) string {
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index := strings.Index(s, refStart)
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for index != -1 {
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endIndex := strings.Index(s, refEnd)
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if endIndex != -1 {
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ref := s[index : endIndex+len(refEnd)]
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s = strings.Replace(s, ref, os.Getenv(ref[len(refStart):len(ref)-len(refEnd)]), -1)
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} else {
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return s
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}
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index = strings.Index(s, refStart)
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}
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return s
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}
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type (
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// ServerBlock associates tokens with a list of addresses
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// and groups tokens by directive name.
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ServerBlock struct {
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Addresses []address
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Tokens map[string][]token
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}
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address struct {
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Original, Host, Port string
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}
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)
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// HostList converts the list of addresses that are
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// associated with this server block into a slice of
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// strings, where each address is as it was originally
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// read from the input.
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func (sb ServerBlock) HostList() []string {
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sbHosts := make([]string, len(sb.Addresses))
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for j, addr := range sb.Addresses {
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sbHosts[j] = addr.Original
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}
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return sbHosts
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}
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