pcap_mm.c

   1 /*
   2  * netsniff-ng - the packet sniffing beast
   3  * By Daniel Borkmann <daniel@netsniff-ng.org>
   4  * Copyright 2011 - 2013 Daniel Borkmann.
   5  * Subject to the GPL, version 2.
   6  */
   7
   8 #define _GNU_SOURCE
   9 #include <stdio.h>
  10 #include <sys/types.h>
  11 #include <sys/stat.h>
  12 #include <fcntl.h>
  13 #include <unistd.h>
  14 #include <stdbool.h>
  15 #include <sys/mman.h>
  16
  17 #include "pcap.h"
  18 #include "xio.h"
  19 #include "xutils.h"
  20 #include "built_in.h"
  21
  22 static size_t map_size = 0;
  23 static char *ptr_va_start, *ptr_va_curr;
  24
  25 static void __pcap_mmap_write_need_remap(int fd)
  26 {
  27         int ret;
  28         off_t pos, map_size_old = map_size;
  29         off_t offset = ptr_va_curr - ptr_va_start;
  30
  31         map_size = PAGE_ALIGN(map_size_old * 10 / 8);
  32
  33         pos = lseek(fd, map_size, SEEK_SET);
  34         if (pos < 0)
  35                 panic("Cannot lseek pcap file!\n");
  36
  37         ret = write_or_die(fd, "", 1);
  38         if (ret != 1)
  39                 panic("Cannot write file!\n");
  40
  41         ptr_va_start = mremap(ptr_va_start, map_size_old, map_size, MREMAP_MAYMOVE);
  42         if (ptr_va_start == MAP_FAILED)
  43                 panic("mmap of file failed!");
  44
  45         ret = madvise(ptr_va_start, map_size, MADV_SEQUENTIAL);
  46         if (ret < 0)
  47                 panic("Failed to give kernel mmap advise!\n");
  48
  49         ptr_va_curr = ptr_va_start + offset;
  50 }
  51
  52 static ssize_t pcap_mm_write(int fd, pcap_pkthdr_t *phdr, enum pcap_type type,
  53                              const uint8_t *packet, size_t len)
  54 {
  55         size_t hdrsize = pcap_get_hdr_length(phdr, type);
  56
  57         if ((off_t) (ptr_va_curr - ptr_va_start) + hdrsize + len > map_size)
  58                 __pcap_mmap_write_need_remap(fd);
  59
  60         fmemcpy(ptr_va_curr, &phdr->raw, hdrsize);
  61         ptr_va_curr += hdrsize;
  62         fmemcpy(ptr_va_curr, packet, len);
  63         ptr_va_curr += len;
  64
  65         return hdrsize + len;
  66 }
  67
  68 static ssize_t pcap_mm_read(int fd, pcap_pkthdr_t *phdr, enum pcap_type type,
  69                             uint8_t *packet, size_t len)
  70 {
  71         size_t hdrsize = pcap_get_hdr_length(phdr, type), hdrlen;
  72
  73         if (unlikely((off_t) (ptr_va_curr + hdrsize - ptr_va_start) > map_size))
  74                 return -EIO;
  75
  76         fmemcpy(&phdr->raw, ptr_va_curr, hdrsize);
  77         ptr_va_curr += hdrsize;
  78         hdrlen = pcap_get_length(phdr, type);
  79
  80         if (unlikely((off_t) (ptr_va_curr + hdrlen - ptr_va_start) > map_size))
  81                 return -EIO;
  82         if (unlikely(hdrlen == 0 || hdrlen > len))
  83                 return -EINVAL;
  84
  85         fmemcpy(packet, ptr_va_curr, hdrlen);
  86         ptr_va_curr += hdrlen;
  87
  88         return hdrsize + hdrlen;
  89 }
  90
  91 static inline off_t ____get_map_size(bool jumbo)
  92 {
  93         int allocsz = jumbo ? 16 : 3;
  94
  95         return PAGE_ALIGN(sizeof(struct pcap_filehdr) + (PAGE_SIZE * allocsz) * 1024);
  96 }
  97
  98 static void __pcap_mm_prepare_access_wr(int fd, bool jumbo)
  99 {
 100         int ret;
 101         off_t pos;
 102         struct stat sb;
 103
 104         map_size = ____get_map_size(jumbo);
 105
 106         ret = fstat(fd, &sb);
 107         if (ret < 0)
 108                 panic("Cannot fstat pcap file!\n");
 109         if (!S_ISREG (sb.st_mode))
 110                 panic("pcap dump file is not a regular file!\n");
 111
 112         pos = lseek(fd, map_size, SEEK_SET);
 113         if (pos < 0)
 114                 panic("Cannot lseek pcap file!\n");
 115
 116         ret = write_or_die(fd, "", 1);
 117         if (ret != 1)
 118                 panic("Cannot write file!\n");
 119
 120         ptr_va_start = mmap(0, map_size, PROT_WRITE, MAP_SHARED, fd, 0);
 121         if (ptr_va_start == MAP_FAILED)
 122                 panic("mmap of file failed!");
 123         ret = madvise(ptr_va_start, map_size, MADV_SEQUENTIAL);
 124         if (ret < 0)
 125                 panic("Failed to give kernel mmap advise!\n");
 126
 127         ptr_va_curr = ptr_va_start + sizeof(struct pcap_filehdr);
 128 }
 129
 130 static void __pcap_mm_prepare_access_rd(int fd)
 131 {
 132         int ret;
 133         struct stat sb;
 134
 135         ret = fstat(fd, &sb);
 136         if (ret < 0)
 137                 panic("Cannot fstat pcap file!\n");
 138         if (!S_ISREG (sb.st_mode))
 139                 panic("pcap dump file is not a regular file!\n");
 140
 141         map_size = sb.st_size;
 142         ptr_va_start = mmap(0, map_size, PROT_READ, MAP_SHARED | MAP_LOCKED, fd, 0);
 143         if (ptr_va_start == MAP_FAILED)
 144                 panic("mmap of file failed!");
 145         ret = madvise(ptr_va_start, map_size, MADV_SEQUENTIAL);
 146         if (ret < 0)
 147                 panic("Failed to give kernel mmap advise!\n");
 148
 149         ptr_va_curr = ptr_va_start + sizeof(struct pcap_filehdr);
 150 }
 151
 152 static int pcap_mm_prepare_access(int fd, enum pcap_mode mode, bool jumbo)
 153 {
 154         set_ioprio_be();
 155
 156         switch (mode) {
 157         case PCAP_MODE_RD:
 158                 __pcap_mm_prepare_access_rd(fd);
 159                 break;
 160         case PCAP_MODE_WR:
 161                 __pcap_mm_prepare_access_wr(fd, jumbo);
 162                 break;
 163         default:
 164                 bug();
 165         }
 166
 167         return 0;
 168 }
 169
 170 static void pcap_mm_fsync(int fd)
 171 {
 172         msync(ptr_va_start, (off_t) (ptr_va_curr - ptr_va_start), MS_ASYNC);
 173 }
 174
 175 static void pcap_mm_prepare_close(int fd, enum pcap_mode mode)
 176 {
 177         int ret;
 178
 179         ret = munmap(ptr_va_start, map_size);
 180         if (ret < 0)
 181                 panic("Cannot unmap the pcap file!\n");
 182
 183         if (mode == PCAP_MODE_WR) {
 184                 ret = ftruncate(fd, (off_t) (ptr_va_curr - ptr_va_start));
 185                 if (ret)
 186                         panic("Cannot truncate the pcap file!\n");
 187         }
 188 }
 189
 190 const struct pcap_file_ops pcap_mm_ops = {
 191         .pull_fhdr_pcap = pcap_generic_pull_fhdr,
 192         .push_fhdr_pcap = pcap_generic_push_fhdr,
 193         .prepare_access_pcap = pcap_mm_prepare_access,
 194         .prepare_close_pcap = pcap_mm_prepare_close,
 195         .read_pcap = pcap_mm_read,
 196         .write_pcap = pcap_mm_write,
 197         .fsync_pcap = pcap_mm_fsync,
 198 };