[*] Initial commit

tools/bgpgrep/bgpgrep_asmatch.c

@@ -0,0 +1,214 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+/**
+ * \file bgpgrep_asmatch.c
+ *
+ * AS_PATH regular expressions compilation.
+ *
+ * \copyright The DoubleFourteen Code Forge (C) All Rights Reserved
+ * \author    Lorenzo Cogotti
+ */
+
+#include "bgpgrep_local.h"
+
+#include "sys/con.h"
+#include "sys/endian.h"
+#include "lexer.h"
+#include "strlib.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+#define MAXEXCERPTLEN 32
+
+#define GROWSTEP 128
+
+typedef struct {
+	unsigned cap, len;
+	Asn      expr[FLEX_ARRAY];
+} Asnbuf;
+
+// Return TRUE if `asn` may be followed by '+', '?' or '*' wildcards.
+static Boolean WildcardAllowed(Asn asn)
+{
+	return asn != ASN_START && asn != ASN_END && asn != ASN_ALT && asn != ASN_NEWGRP;
+}
+
+static void AddAsnToList(Asnbuf **pbuf, Asn asn)
+{
+	Asnbuf *buf = *pbuf;
+
+	if (!buf || buf->len == buf->cap) {
+		size_t oldcap = buf ? buf->cap : 0;
+		size_t newcap = oldcap + GROWSTEP;
+
+		buf = (Asnbuf *) realloc(buf, offsetof(Asnbuf, expr[newcap]));
+		if (!buf)
+			Bgpgrep_Fatal("Memory allocation failure");
+
+		buf->cap = newcap;
+		buf->len = oldcap;
+
+		*pbuf = buf;
+	}
+
+	buf->expr[buf->len++] = asn;
+}
+
+Sint32 BgpgrepC_BakeAsRegexp(void)
+{
+	// Generate expression name
+	char expnam[1 + 16 + MAXEXCERPTLEN + 1 + 1], *ptr = expnam;
+
+	const char *match = BgpgrepC_ExpectAnyToken();
+
+	*ptr++ = '<';
+
+	strcpy(ptr, "AS PATH regexp: "); ptr += 16;
+
+	size_t n = Df_strncpyz(ptr, match, MAXEXCERPTLEN);
+	if (n > MAXEXCERPTLEN) strcpy(ptr + MAXEXCERPTLEN-3, "...");
+
+	ptr += n;
+
+	*ptr++ = '>';
+	*ptr   = '\0';
+
+	// Setup lexer
+	Lex p;
+	Tok tok;
+
+	memset(&p, 0, sizeof(p));
+	if (!S.noColor)
+		SetLexerFlags(&p, L_COLORED);
+
+	BeginLexerSession(&p, expnam, /*line=*/1);
+	SetLexerTextn(&p, match, n);
+	SetLexerErrorFunc(&p, LEX_QUIT, LEX_WARN, NULL);
+
+	// Compile expression
+	Asnbuf *buf = NULL;
+
+	int notcount = 0;
+	int nparens = 0;
+	Boolean seenAsn = FALSE, seenBol = FALSE, seenEol = FALSE;
+	Boolean wUnmatchable = TRUE;
+	Asn asn;
+
+	while (Lex_ReadToken(&p, &tok)) {
+		// Special handling for negation (don't produce any ASN)
+		if (strcmp(tok.text, "!") == 0) {
+			notcount++;
+			continue;
+		}
+
+		// Any other case
+		if (strcmp(tok.text, "(") == 0) {
+			if (notcount > 0)
+				LexerError(&p, "Illegal '(' after '!' ASN modifier");
+
+			AddAsnToList(&buf, ASN_NEWGRP);
+			seenBol = seenAsn = seenEol = FALSE;
+			wUnmatchable = TRUE;
+			nparens++;
+		} else if (strcmp(tok.text, ")") == 0) {
+			if (notcount > 0)
+				LexerError(&p, "Dangling '!' at end of group");
+			if (nparens == 0)
+				LexerError(&p, "Stray ')' in match expression");
+
+			AddAsnToList(&buf, ASN_ENDGRP);
+			seenBol = seenAsn = seenEol = FALSE;
+			wUnmatchable = TRUE;
+			nparens--;
+		} else if (strcmp(tok.text, "^") == 0) {
+			if (notcount > 0)
+				LexerError(&p, "Illegal '^' after '!' ASN modifier");
+			if (seenBol)
+				LexerWarning(&p, "Duplicate '^'");
+			if (seenAsn && wUnmatchable) {
+				LexerWarning(&p, "'^' following ASN term never matches");
+				wUnmatchable = FALSE;
+			}
+			if (seenEol && wUnmatchable) {
+				LexerWarning(&p, "'^' following '$' never matches");
+				wUnmatchable = FALSE;
+			}
+
+			AddAsnToList(&buf, ASN_START);
+			seenBol = TRUE;
+		} else if (strcmp(tok.text, "$") == 0) {
+			if (notcount > 0)
+				LexerError(&p, "Illegal '$' after '!' ASN modifier");
+			if (seenEol)
+				LexerWarning(&p, "Duplicate '$'");
+
+			AddAsnToList(&buf, ASN_END);
+			seenEol = TRUE;
+		} else if (strcmp(tok.text, "|") == 0) {
+			if (notcount > 0)
+				LexerError(&p, "Alternative not allowed after '!'");
+
+			AddAsnToList(&buf, ASN_ALT);
+			seenBol = seenAsn = seenEol = FALSE;
+			wUnmatchable = TRUE;
+		} else {
+			if (strcmp(tok.text, ".") == 0) {
+				// Any match, make sure ! wasn't used
+				if (notcount > 0)
+					LexerError(&p, "Illegal use of '!' combined with '.' operator");
+
+				asn = ASN_ANY;
+
+			} else {
+				// Read actual numeric ASN
+				Lex_UngetToken(&p, &tok);
+
+				long long num = Lex_ParseInt(&p, /*optionalSign=*/FALSE);
+				if (num > 0xffffffff)
+					LexerError(&p, "%lld: ASN is out of range", num);
+
+				asn = ASN32BIT(beswap32(num));
+			}
+
+			if (notcount & 1)
+				asn = ASNNOT(asn);  // negate match
+
+			if (seenEol && wUnmatchable) {
+				LexerWarning(&p, "ASN term following '$' never matches");
+				wUnmatchable = FALSE;
+			}
+
+			AddAsnToList(&buf, asn);
+			notcount = 0;
+
+			seenAsn = TRUE;
+		}
+
+		// Allow *, ? and + repetition operators
+		if (WildcardAllowed(buf->expr[buf->len-1])) {
+			if (Lex_CheckToken(&p, "*"))
+				AddAsnToList(&buf, ASN_STAR);
+			else if (Lex_CheckToken(&p, "+"))
+				AddAsnToList(&buf, ASN_PLUS);
+			else if (Lex_CheckToken(&p, "?"))
+				AddAsnToList(&buf, ASN_QUEST);
+		}
+	}
+	if (nparens != 0)
+		LexerError(&p, "Missing ')' at end of match expression");
+	if (notcount != 0)
+		LexerError(&p, "Dangling '!' at end of match expression");
+
+	void *regexp = Bgp_VmCompileAsMatch(&S.vm, buf->expr, buf->len);
+	if (!regexp)
+		Bgpgrep_Fatal("AS PATH Regexp compilation failed");
+
+	Sint32 kidx = BGP_VMSETKA(&S.vm, Bgp_VmNewk(&S.vm), regexp);
+	if (kidx == -1)
+		Bgpgrep_Fatal("Maximum BGP VM variables limit hit: please try to simplify the filtering expression");
+
+	free(buf);
+
+	return kidx;
+}