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https://github.com/PHJArea217/socket-enhancer
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Initial commit
This commit is contained in:
Peter H. Jin
commit
1dd53e792d
284
socket-enhancer.c
Normal file
284
socket-enhancer.c
Normal file
@ -0,0 +1,284 @@
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#define _GNU_SOURCE
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#include <stdio.h>
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#include <stdlib.h>
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#include <arpa/inet.h>
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#include <sys/socket.h>
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#include <string.h>
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#include <netinet/in.h>
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#include <net/if.h>
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#include <dlfcn.h>
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struct ipv6_with_scope {
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struct in6_addr address;
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uint32_t scope_id;
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};
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static int parse_ipv6_with_scope(char *str, struct ipv6_with_scope *result) {
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char *percent_brk = strchr(str, '%');
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if (percent_brk) {
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char *interface_name = &percent_brk[1];
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*percent_brk = 0;
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uint32_t index;
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if ((interface_name[0] >= '0') && (interface_name[0] <= '9')) {
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index = strtoul(interface_name, NULL, 0);
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} else {
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index = if_nametoindex(interface_name);
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if (!index) return -1;
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}
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struct in6_addr res_addr = {0};
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if (inet_pton(AF_INET6, str, &res_addr) != 1) return -1;
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result->scope_id = index;
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memcpy(&result->address, &res_addr, sizeof(struct in6_addr));
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} else {
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int results = inet_pton(AF_INET6, str, &result->address);
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if (results != 1) return -1;
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result->scope_id = 0;
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}
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return 0;
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}
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struct socket_enhancer_config {
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int (*real_bind)(int, const struct sockaddr *, socklen_t);
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int (*real_connect)(int, const struct sockaddr *, socklen_t);
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struct in_addr ipv4_default;
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struct in_addr ipv4_loopback;
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uint8_t universal_link_local_mode;
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uint8_t always_freebind;
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uint8_t has_v4_default:1;
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uint8_t has_v4_loopback:1;
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uint8_t has_v6_default:1;
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uint8_t has_v6_v4mapv6:1;
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uint8_t has_v6_linklocal:1;
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struct ipv6_with_scope ipv6_default;
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struct ipv6_with_scope ipv6_v4mapv6;
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struct ipv6_with_scope ipv6_linklocal;
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};
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static struct socket_enhancer_config *global_config = NULL;
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static void parse_v4(const char *addr, struct in_addr *result) {
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if (inet_pton(AF_INET, addr, result) != 1) {
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fprintf(stderr, "Invalid IPv4 address %s\n", addr);
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abort();
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}
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}
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static void parse_v6(char *addr, struct ipv6_with_scope *result) {
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if (parse_ipv6_with_scope(addr, result)) {
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fprintf(stderr, "Invalid IPv6 address %s\n", addr);
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abort();
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}
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}
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__attribute__((constructor))
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static void socket_enhancer_init(void) {
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void *real_bind_p = dlsym(RTLD_NEXT, "bind");
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if (!real_bind_p) abort();
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void *real_connect_p = dlsym(RTLD_NEXT, "connect");
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if (!real_connect_p) abort();
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struct socket_enhancer_config *temp_config = calloc(sizeof(struct socket_enhancer_config), 1);
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if (!temp_config) abort();
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temp_config->real_bind = real_bind_p;
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temp_config->real_connect = real_connect_p;
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const char *config_str = getenv("SOCKET_ENHANCER_CONFIG");
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if (config_str) {
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char *dup_configstr = strdup(config_str);
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if (!dup_configstr) abort();
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char *saveptr = NULL;
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for (char *token = strtok_r(dup_configstr, ",", &saveptr); token; token = strtok_r(NULL, ",", &saveptr)) {
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if (strnlen(token, 5) < 5) {
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fprintf(stderr, "Invalid config option %s\n", token);
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abort();
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return;
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}
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if (token[4] != '=') {
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fprintf(stderr, "Config option must be name=value\n");
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abort();
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return;
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}
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uint32_t option = ntohl(*(uint32_t *) token);
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token[4] = 0;
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char *value = &token[5];
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unsigned long option_numeric_value = 0;
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switch (option) {
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case 0x69707634: /* "ipv4" */
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parse_v4(value, &temp_config->ipv4_default);
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temp_config->has_v4_default = 1;
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break;
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case 0x76346c62: /* "v4lb" */
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parse_v4(value, &temp_config->ipv4_loopback);
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temp_config->has_v4_loopback = 1;
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break;
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case 0x69707636: /* "ipv6" */
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parse_v6(value, &temp_config->ipv6_default);
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temp_config->has_v6_default = 1;
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break;
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case 0x76366c6c: /* "v6ll" */
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parse_v6(value, &temp_config->ipv6_linklocal);
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temp_config->has_v6_linklocal = 1;
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break;
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case 0x76346d36: /* "v4m6" */
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parse_v6(value, &temp_config->ipv6_v4mapv6);
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temp_config->has_v6_v4mapv6 = 1;
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break;
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case 0x7636756c: /* "v6ul" */
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option_numeric_value = strtoul(value, NULL, 0);
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if (option_numeric_value > 3) goto out_of_range;
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temp_config->universal_link_local_mode = option_numeric_value;
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break;
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case 0x66726562: /* "freb" */
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option_numeric_value = strtoul(value, NULL, 0);
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if (option_numeric_value > 3) goto out_of_range;
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temp_config->always_freebind = option_numeric_value;
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break;
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default:
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fprintf(stderr, "Invalid config option %s\n", token);
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abort();
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return;
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}
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continue;
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out_of_range:
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fprintf(stderr, "Value %lu for %s out of range\n", option_numeric_value, token);
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abort();
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return;
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}
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free(dup_configstr);
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}
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__atomic_store_n(&global_config, temp_config, __ATOMIC_SEQ_CST);
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}
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static void convert_universal_linklocal(struct sockaddr_in6 *addr) {
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if (!addr->sin6_scope_id) {
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#if __BYTE_ORDER == __LITTLE_ENDIAN
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if (addr->sin6_addr.s6_addr32[0] == 0x000090fe) {
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addr->sin6_addr.s6_addr32[0] = 0x000080fe;
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#else
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if (addr->sin6_addr.s6_addr32[0] == 0xfe900000) {
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addr->sin6_addr.s6_addr32[0] = 0xfe800000;
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#endif
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addr->sin6_scope_id = ntohl(addr->sin6_addr.s6_addr32[1]);
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addr->sin6_addr.s6_addr32[1] = 0;
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}
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}
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#if 0
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}
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#endif
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}
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static int try_preconnect_bind_v4(int fd, const struct in_addr *bind_addr, int freebind, struct socket_enhancer_config *config) {
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struct sockaddr_in existing_address = {0};
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socklen_t addrlen = sizeof(struct sockaddr_in);
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if (getsockname(fd, (struct sockaddr *) &existing_address, &addrlen)) return -1;
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if (addrlen == sizeof(struct sockaddr_in)) {
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if (existing_address.sin_family == AF_INET) {
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if (*(uint32_t *) &existing_address.sin_addr) return 0;
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}
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}
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int one = 1;
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setsockopt(fd, SOL_IP, IP_BIND_ADDRESS_NO_PORT, &one, sizeof(one));
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one = 1;
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if (freebind) setsockopt(fd, SOL_IP, IP_FREEBIND, &one, sizeof(one));
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memset(&existing_address, 0, sizeof(existing_address));
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existing_address.sin_family = AF_INET;
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memcpy(&existing_address.sin_addr, bind_addr, sizeof(struct in_addr));
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return config->real_bind(fd, (struct sockaddr *) &existing_address, sizeof(existing_address));
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}
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static int try_preconnect_bind_v6(int fd, const struct ipv6_with_scope *bind_addr, int freebind, struct socket_enhancer_config *config) {
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struct sockaddr_in6 existing_address = {0};
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socklen_t addrlen = sizeof(struct sockaddr_in6);
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if (getsockname(fd, (struct sockaddr *) &existing_address, &addrlen)) return -1;
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if (addrlen == sizeof(struct sockaddr_in6)) {
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if (existing_address.sin6_family == AF_INET6) {
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if (existing_address.sin6_addr.s6_addr32[0]) return 0;
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if (existing_address.sin6_addr.s6_addr32[1]) return 0;
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if (existing_address.sin6_addr.s6_addr32[2]) return 0;
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if (existing_address.sin6_addr.s6_addr32[3]) return 0;
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}
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}
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int one = 1;
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setsockopt(fd, SOL_IP, IP_BIND_ADDRESS_NO_PORT, &one, sizeof(one));
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one = 1;
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if (freebind) setsockopt(fd, SOL_IP, IP_FREEBIND, &one, sizeof(one));
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memset(&existing_address, 0, sizeof(existing_address));
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existing_address.sin6_family = AF_INET6;
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memcpy(&existing_address.sin6_addr, &bind_addr->address, sizeof(struct in6_addr));
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existing_address.sin6_scope_id = bind_addr->scope_id;
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return config->real_bind(fd, (struct sockaddr *) &existing_address, sizeof(existing_address));
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}
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int connect(int fd, const struct sockaddr *addr_, socklen_t len_) {
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const struct sockaddr *addr = addr_;
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socklen_t len = len_;
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union {
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struct sockaddr_in ipv4_addr;
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struct sockaddr_in6 ipv6_addr;
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} new_addr;
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memset(&new_addr, 0, sizeof(new_addr));
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struct socket_enhancer_config *config = __atomic_load_n(&global_config, __ATOMIC_SEQ_CST);
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if (!config) abort();
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int always_freebind = !!(config->always_freebind & 2);
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if (len == sizeof(struct sockaddr_in6)) {
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if (addr->sa_family == AF_INET6) {
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const struct ipv6_with_scope *bind_addr = NULL;
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struct ipv6_with_scope tmp_addr = {0};
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memcpy(&new_addr.ipv6_addr, addr, sizeof(struct sockaddr_in6));
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addr = (struct sockaddr *) &new_addr.ipv6_addr;
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if (IN6_IS_ADDR_LINKLOCAL(&new_addr.ipv6_addr.sin6_addr)) {
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if (config->universal_link_local_mode & 2) {
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convert_universal_linklocal(&new_addr.ipv6_addr);
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}
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if (config->has_v6_linklocal) {
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bind_addr = &config->ipv6_linklocal;
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if (IN6_IS_ADDR_UNSPECIFIED(&bind_addr->address) && bind_addr->scope_id) {
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if (!new_addr.ipv6_addr.sin6_scope_id) {
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new_addr.ipv6_addr.sin6_scope_id = bind_addr->scope_id;
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}
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bind_addr = NULL;
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}
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} else if (config->has_v6_default) {
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bind_addr = &config->ipv6_default;
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}
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} else if (IN6_IS_ADDR_V4MAPPED(&new_addr.ipv6_addr.sin6_addr)) {
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if (config->has_v6_v4mapv6) {
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bind_addr = &config->ipv6_v4mapv6;
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} else if (config->has_v4_default) {
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tmp_addr.address.s6_addr16[4] = 0;
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tmp_addr.address.s6_addr16[5] = 0xffff;
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tmp_addr.address.s6_addr32[3] = *(uint32_t *) &config->ipv4_default;
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bind_addr = &tmp_addr;
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}
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} else {
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if (config->has_v6_default) {
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bind_addr = &config->ipv6_default;
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}
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}
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if (bind_addr) {
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if (try_preconnect_bind_v6(fd, bind_addr, always_freebind, config)) return -1;
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}
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}
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} else if (len == sizeof(struct sockaddr_in)) {
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if (addr->sa_family == AF_INET) {
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memcpy(&new_addr.ipv4_addr, addr, sizeof(struct sockaddr_in));
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addr = (struct sockaddr *) &new_addr.ipv4_addr;
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struct in_addr *v4_address = &new_addr.ipv4_addr.sin_addr;
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if ((config->has_v4_loopback) && ((ntohl(v4_address->s_addr) & 0xff000000) == 0x7f000000)) {
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if (try_preconnect_bind_v4(fd, &config->ipv4_loopback, always_freebind, config)) return -1;
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} else if (config->has_v4_default) {
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if (try_preconnect_bind_v4(fd, &config->ipv4_default, always_freebind, config)) return -1;
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}
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}
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}
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return config->real_connect(fd, addr, len);
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}
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int bind(int fd, const struct sockaddr *addr_, socklen_t len_) {
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struct socket_enhancer_config *config = __atomic_load_n(&global_config, __ATOMIC_SEQ_CST);
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if (!config) abort();
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int always_freebind = !!(config->always_freebind & 1);
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const struct sockaddr *addr = addr_;
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socklen_t len = len_;
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struct sockaddr_in6 ipv6_addr = {0};
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if (len == sizeof(struct sockaddr_in6)) {
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if (addr->sa_family == AF_INET6) {
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memcpy(&ipv6_addr, addr, sizeof(struct sockaddr_in6));
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addr = (struct sockaddr *) &ipv6_addr;
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if (config->universal_link_local_mode & 1) {
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convert_universal_linklocal(&ipv6_addr);
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}
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}
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}
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if (always_freebind) {
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int one = 1;
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setsockopt(fd, SOL_IP, IP_FREEBIND, &one, sizeof(one));
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}
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return config->real_bind(fd, addr, len);
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}
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