src/bpf_hla_parser.y

   1 /*
   2  * netsniff-ng - the packet sniffing beast
   3  * By Daniel Borkmann <daniel@netsniff-ng.org>
   4  * Copyright 2012 Daniel Borkmann <dborkma@tik.ee.ethz.ch>,
   5  * Swiss federal institute of technology (ETH Zurich)
   6  * Subject to the GPL, version 2.
   7  */
   8
   9 %{
  10
  11 #include <stdio.h>
  12 #include <stdlib.h>
  13 #include <stdbool.h>
  14 #include <stdint.h>
  15 #include <errno.h>
  16
  17 #include "bpf.h"
  18 #include "bpf_hla_parser.tab.h"
  19 #include "bpf_symtab.h"
  20 #include "xmalloc.h"
  21 #include "xutils.h"
  22 #include "built_in.h"
  23 #include "die.h"
  24
  25 #define YYERROR_VERBOSE         0
  26 #define YYDEBUG                 0
  27 #define YYENABLE_NLS            1
  28 #define YYLTYPE_IS_TRIVIAL      1
  29 #define ENABLE_NLS              1
  30
  31 extern FILE *zzin;
  32 extern int zzlex(void);
  33 extern void zzerror(const char *);
  34 extern int zzlineno;
  35 extern char *zztext;
  36
  37 int compile_hla_filter(char *file, int verbose, int debug);
  38
  39 static unsigned int num_vars = 0;
  40
  41 %}
  42
  43 %union {
  44         int idx;
  45         long int number;
  46 }
  47
  48 %token K_NAME K_DEF K_PKT K_RET K_IF K_ELIF K_ELSE
  49 %token K_MACRO_IPV4 K_MACRO_IPV6 K_MACRO_IP K_MACRO_UDP K_MACRO_TCP
  50
  51 %token '(' ')' '{' '}' '=' ';' '+' '-' '&' '|' '^' '!' '<' '>' '*' '/' '%' ','
  52
  53 %token number_hex number_dec number_oct number_bin
  54
  55 %type <idx> K_NAME var
  56 %type <number> number_hex number_dec number_oct number_bin number
  57
  58 %%
  59
  60 program
  61         : declaration_list statement_list
  62         | short_ret /* for short filter statements */
  63         ;
  64
  65 declaration_list
  66         : declaration ';' { num_vars++; } declaration_list
  67         | /* empty */
  68         ;
  69
  70 statement_list
  71         : statement ';' statement_list
  72         | block statement_list
  73         | /* empty */
  74         ;
  75
  76 declaration
  77         : K_DEF K_NAME {
  78                 if (bpf_symtab_declared($2)) {
  79                         panic("Variable \"%s\" already declared (l%d)\n",
  80                               bpf_symtab_name($2), zzlineno);
  81                 } else {
  82                         printf("; @var %s\n", bpf_symtab_name($2));
  83                         bpf_symtab_declare($2);
  84                 }}
  85         ;
  86
  87 block
  88         : condition
  89         ;
  90
  91 statement
  92         : assignment
  93         | return
  94         ;
  95
  96 short_ret
  97         : expression
  98         ;
  99
 100 return
 101         : K_RET { printf("ret a\n"); }
 102         | K_RET number { printf("ret #%ld\n", $2); }
 103         | K_RET var { printf("ret a\n"); }
 104         | K_RET expression { printf("ret macro\n"); }
 105         ;
 106
 107 macro
 108         : K_MACRO_IPV4 { printf("ipv4\n"); }
 109         | K_MACRO_IPV6 { printf("ipv6\n"); }
 110         | K_MACRO_IP { printf("ip\n"); }
 111         | K_MACRO_UDP { printf("udp\n"); }
 112         | K_MACRO_TCP { printf("tcp\n"); }
 113         ;
 114
 115 condition
 116         : K_IF '(' expression ')' '{' statement_list '}' condition_contd
 117         ;
 118
 119 condition_contd
 120         : K_ELIF '(' expression ')' '{' statement_list '}' condition_contd
 121         | K_ELSE '{' statement_list '}'
 122         | /* None */
 123         ;
 124
 125 assignment
 126         : var '=' expression { printf("; @asn %s\n", bpf_symtab_name($1)); }
 127         | var '=' K_PKT '(' number ',' number ')' {
 128                         switch ($7) {
 129                         case 1:
 130                                 printf("ldb [%ld]\n", $5);
 131                                 break;
 132                         case 2:
 133                                 printf("ldh [%ld]\n", $5);
 134                                 break;
 135                         case 4:
 136                                 printf("ld [%ld]\n", $5);
 137                                 break;
 138                         default:
 139                                 panic("Invalid argument (l%d)\n", zzlineno);
 140                         }
 141                 }
 142         ;
 143
 144 expression
 145         : term
 146         | '!' term { printf("; @!\n"); }
 147         | term '+' term { printf("; @+\n"); }
 148         | term '-' term { printf("; @-\n"); }
 149         | term '/' term { printf("; @/\n"); }
 150         | term '*' term { printf("; @*\n"); }
 151         | term '%' term { printf("; @\n"); }
 152         | term '&' term { printf("; @&\n"); }
 153         | term '|' term { printf("; @|\n"); }
 154         | term '^' term { printf("; @^\n"); }
 155         | term '<' term { printf("; @<\n"); }
 156         | term '>' term { printf("; @>\n"); }
 157         | term '=' '=' term { printf("; @==\n"); }
 158         | term '&' '&' term { printf("; @&&\n"); }
 159         | term '|' '|' term { printf("; @||\n"); }
 160         | term '<' '<' term { printf("; @<<\n"); }
 161         | term '>' '>' term { printf("; @>>\n"); }
 162         ;
 163
 164 term
 165         : number { printf("; @num %ld\n", $1); }
 166         | var { printf("; @var %s\n", bpf_symtab_name($1)); }
 167         | macro
 168         | '(' expression ')'
 169         ;
 170
 171 var
 172         : K_NAME {
 173                 if (!bpf_symtab_declared($1))
 174                         panic("Variable \"%s\" not declared (l%d)\n",
 175                               bpf_symtab_name($1), zzlineno);
 176                 $$ = $1; }
 177         ;
 178
 179 number
 180         : number_dec { $$ = $1; }
 181         | number_hex { $$ = $1; }
 182         | number_oct { $$ = $1; }
 183         | number_bin { $$ = $1; }
 184         ;
 185
 186 %%
 187
 188 static void stage_1_compile(void)
 189 {
 190         zzparse();
 191 }
 192
 193 int compile_hla_filter(char *file, int verbose, int debug)
 194 {
 195         int fd;
 196         fpos_t pos;
 197         char file_tmp[128];
 198
 199         if (!strncmp("-", file, strlen("-")))
 200                 zzin = stdin;
 201         else
 202                 zzin = fopen(file, "r");
 203         if (!zzin)
 204                 panic("Cannot open file!\n");
 205         if (!debug) {
 206                 fd = dup(fileno(stdout));
 207
 208                 slprintf(file_tmp, sizeof(file_tmp), ".%s", file);
 209                 if (freopen(file_tmp, "w", stdout) == NULL)
 210                         panic("Cannot reopen file!\n");
 211         }
 212
 213         stage_1_compile();
 214
 215         if (!debug) {
 216                 fflush(stdout);
 217                 dup2(fd, fileno(stdout));
 218
 219                 close(fd);
 220                 clearerr(stdout);
 221                 fsetpos(stdout, &pos);
 222         }
 223
 224         fclose(zzin);
 225
 226         bpf_symtab_cleanup();
 227         if (debug)
 228                 die();
 229
 230         return 0;
 231 }
 232
 233 void zzerror(const char *err)
 234 {
 235         panic("Syntax error at line %d: %s! %s!\n",
 236               zzlineno, zztext, err);
 237 }