diff options
Diffstat (limited to 'src/network/res_msend.c')
| -rw-r--r-- | src/network/res_msend.c | 184 |
1 files changed, 184 insertions, 0 deletions
diff --git a/src/network/res_msend.c b/src/network/res_msend.c new file mode 100644 index 00000000..cded5353 --- /dev/null +++ b/src/network/res_msend.c @@ -0,0 +1,184 @@ +#include <sys/socket.h> +#include <netinet/in.h> +#include <netdb.h> +#include <arpa/inet.h> +#include <stdint.h> +#include <string.h> +#include <poll.h> +#include <time.h> +#include <ctype.h> +#include <unistd.h> +#include <errno.h> +#include <pthread.h> +#include "stdio_impl.h" +#include "syscall.h" + +static void cleanup(void *p) +{ + __syscall(SYS_close, (intptr_t)p); +} + +static unsigned long mtime() +{ + struct timespec ts; + clock_gettime(CLOCK_REALTIME, &ts); + return (unsigned long)ts.tv_sec * 1000 + + ts.tv_nsec / 1000000; +} + +int __res_msend(int nqueries, const unsigned char *const *queries, + const int *qlens, unsigned char *const *answers, int *alens, int asize) +{ + int fd; + FILE *f, _f; + unsigned char _buf[256]; + char line[64], *s, *z; + int timeout = 5000, attempts = 2, retry_interval; + union { + struct sockaddr_in sin; + struct sockaddr_in6 sin6; + } sa = {0}, ns[3] = {{0}}; + socklen_t sl = sizeof sa.sin; + int nns = 0; + int family = AF_INET; + int rlen; + int next; + int i, j; + int cs; + struct pollfd pfd; + unsigned long t0, t1, t2; + + pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs); + + /* Get nameservers from resolv.conf, fallback to localhost */ + f = __fopen_rb_ca("/etc/resolv.conf", &_f, _buf, sizeof _buf); + if (f) for (nns=0; nns<3 && fgets(line, sizeof line, f); ) { + if (!strncmp(line, "options", 7) && isspace(line[7])) { + unsigned long x; + char *p, *z; + p = strstr(line, "timeout:"); + if (p && isdigit(p[8])) { + p += 8; + x = strtoul(p, &z, 10); + if (z != p) timeout = x < 30 ? x*1000 : 30000; + } + p = strstr(line, "attempts:"); + if (p && isdigit(p[9])) { + p += 9; + x = strtoul(p, &z, 10); + if (z != p) attempts = x < 10 ? x : 10; + if (!attempts) attempts = 1; + } + } + if (strncmp(line, "nameserver", 10) || !isspace(line[10])) + continue; + for (s=line+11; isspace(*s); s++); + for (z=s; *z && !isspace(*z); z++); + *z=0; + + if (inet_pton(AF_INET, s, &ns[nns].sin.sin_addr)>0) { + ns[nns].sin.sin_port = htons(53); + ns[nns++].sin.sin_family = AF_INET; + } else if (inet_pton(AF_INET6, s, &ns[nns].sin6.sin6_addr)>0) { + sl = sizeof sa.sin6; + ns[nns].sin6.sin6_port = htons(53); + ns[nns++].sin6.sin6_family = family = AF_INET6; + } + } + if (f) __fclose_ca(f); + if (!nns) { + ns[0].sin.sin_family = AF_INET; + ns[0].sin.sin_port = htons(53); + ns[0].sin.sin_addr.s_addr = htonl(0x7f000001); + nns=1; + } + + /* Get local address and open/bind a socket */ + sa.sin.sin_family = family; + fd = socket(family, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0); + + /* Handle case where system lacks IPv6 support */ + if (fd < 0 && family == AF_INET6 && errno == EAFNOSUPPORT) { + fd = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0); + family = AF_INET; + } + if (fd < 0 || bind(fd, (void *)&sa, sl) < 0) return -1; + + /* Past this point, there are no errors. Each individual query will + * yield either no reply (indicated by zero length) or an answer + * packet which is up to the caller to interpret. */ + + pthread_cleanup_push(cleanup, (void *)(intptr_t)fd); + pthread_setcancelstate(cs, 0); + + /* Convert any IPv4 addresses in a mixed environment to v4-mapped */ + if (family == AF_INET6) { + setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &(int){0}, sizeof 0); + for (i=0; i<nns; i++) { + if (ns[i].sin.sin_family != AF_INET) continue; + memcpy(ns[i].sin6.sin6_addr.s6_addr+12, + &ns[i].sin.sin_addr, 4); + memcpy(ns[i].sin6.sin6_addr.s6_addr, + "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12); + ns[i].sin6.sin6_family = AF_INET6; + ns[i].sin6.sin6_flowinfo = 0; + ns[i].sin6.sin6_scope_id = 0; + } + } + + memset(alens, 0, sizeof *alens * nqueries); + + pfd.fd = fd; + pfd.events = POLLIN; + retry_interval = timeout / attempts; + t0 = t2 = mtime(); + t1 = t2 - retry_interval; + + for (; t2-t0 < timeout; t2=mtime()) { + if (t2-t1 >= retry_interval) { + /* Query all configured namservers in parallel */ + for (i=0; i<nqueries; i++) + if (!alens[i]) + for (j=0; j<nns; j++) + sendto(fd, queries[i], + qlens[i], MSG_NOSIGNAL, + (void *)&ns[j], sl); + t1 = t2; + } + + /* Wait for a response, or until time to retry */ + if (poll(&pfd, 1, t1+retry_interval-t2) <= 0) continue; + + while ((rlen = recvfrom(fd, answers[next], asize, 0, + (void *)&sa, (socklen_t[1]){sl})) >= 0) { + + /* Ignore non-identifiable packets (no query id) */ + if (rlen < 2) continue; + + /* Ignore replies from addresses we didn't send to */ + for (i=0; i<nns && memcmp(ns+i, &sa, sl); i++); + if (i==nns) continue; + + /* Find which query this answer goes with, if any */ + for (i=next; i<nqueries && ( + answers[next][0] != queries[i][0] || + answers[next][1] != queries[i][1] ); i++); + if (i==nqueries) continue; + if (alens[i]) continue; + + /* Store answer in the right slot, or update next + * available temp slot if it's already in place. */ + alens[i] = rlen; + if (i == next) + for (; next<nqueries && alens[next]; next++); + else + memcpy(answers[i], answers[next], rlen); + + if (next == nqueries) goto out; + } + } +out: + pthread_cleanup_pop(1); + + return 0; +} |