ubgpsuite/tools/bgpgrep/bgpgrep_asmatch.c

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2021-06-07 16:55:13 +02:00
// 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;
}