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socket-enhancer
mirror of https://github.com/PHJArea217/socket-enhancer
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socket-enhancer/socket-enhancer.c

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#define _GNU_SOURCE
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <string.h>
#include <netinet/in.h>
#include <net/if.h>
#include <dlfcn.h>
#include <unistd.h>
struct ipv6_with_scope {
struct in6_addr address;
uint32_t scope_id;
};
struct bind_profile {
uint16_t idx;
uint8_t has_if:1;
uint8_t has_if_name:1;
uint8_t has_fwmark:1;
uint8_t set_transparent:1;
uint8_t has_bind_address:1;
uint32_t fwmark;
union {
char *ifname;
uint32_t ifindex;
} bind_interface;
struct in6_addr bind_address;
};
struct socket_enhancer_config {
int (*real_bind)(int, const struct sockaddr *, socklen_t);
int (*real_connect)(int, const struct sockaddr *, socklen_t);
int (*real_socket)(int, int, int);
struct in_addr ipv4_default;
struct in_addr ipv4_loopback;
uint8_t universal_link_local_mode;
uint8_t always_freebind;
uint8_t has_v4_default:1;
uint8_t has_v4_loopback:1;
uint8_t has_v6_default:1;
uint8_t has_v6_v4mapv6:1;
uint8_t has_v6_linklocal:1;
uint8_t has_v6_uniquelocal:1;
uint8_t has_bp_high:1;
struct ipv6_with_scope ipv6_default;
struct ipv6_with_scope ipv6_v4mapv6;
struct ipv6_with_scope ipv6_linklocal;
struct ipv6_with_scope ipv6_uniquelocal;
struct bind_profile *bind_profile_head;
size_t bind_profile_size;
};
static int handle_bind_profile(int socket_fd, const struct bind_profile *profile, int do_bind_address, uint16_t port, struct socket_enhancer_config *config) {
if (profile->has_fwmark) {
if (setsockopt(socket_fd, SOL_SOCKET, SO_MARK, &profile->fwmark, sizeof(uint32_t))) return -1;
}
if (profile->set_transparent) {
int one = 1;
if (setsockopt(socket_fd, SOL_IP, IP_TRANSPARENT, &one, sizeof(one))) {
return -1;
}
}
if (profile->has_if) {
if (profile->has_if_name) {
if (setsockopt(socket_fd, SOL_SOCKET, SO_BINDTODEVICE, profile->bind_interface.ifname, strlen(profile->bind_interface.ifname) + 1)) {
return -1;
}
} else {
if (setsockopt(socket_fd, SOL_SOCKET, SO_BINDTOIFINDEX, &profile->bind_interface.ifindex, sizeof(uint32_t))) {
return -1;
}
}
}
if (do_bind_address && profile->has_bind_address) {
if (port == 0) {
int one = 1;
setsockopt(socket_fd, SOL_IP, IP_BIND_ADDRESS_NO_PORT, &one, sizeof(one));
}
struct sockaddr_in new_bind_addr = {};
struct sockaddr_in6 new_bind_addr6 = {};
int sock_type = AF_UNSPEC;
socklen_t sock_type_len = sizeof(int);
if (getsockopt(socket_fd, SOL_SOCKET, SO_DOMAIN, &sock_type, &sock_type_len)) return -1;
if (sock_type_len != sizeof(int)) return -1;
switch (sock_type) {
case AF_INET:
if (IN6_IS_ADDR_V4MAPPED(&profile->bind_address)) {
new_bind_addr.sin_family = AF_INET;
new_bind_addr.sin_port = port;
new_bind_addr.sin_addr.s_addr = profile->bind_address.s6_addr32[3];
if (config->real_bind(socket_fd, (struct sockaddr *) &new_bind_addr, sizeof(new_bind_addr))) return -1;
} else {
errno = EADDRNOTAVAIL;
return -1;
}
break;
case AF_INET6:
new_bind_addr6.sin6_family = AF_INET6;
new_bind_addr6.sin6_port = port;
memcpy(&new_bind_addr6.sin6_addr, &profile->bind_address, sizeof(struct in6_addr));
if (config->real_bind(socket_fd, (struct sockaddr *) &new_bind_addr6, sizeof(new_bind_addr6))) return -1;
break;
default:
errno = ENOPROTOOPT;
return -1;
}
}
return 0;
}
static int compare_bind_profiles(const void *first, const void *second) {
struct bind_profile *a = (struct bind_profile *) first;
struct bind_profile *b = (struct bind_profile *) second;
if (a->idx < b->idx) return -1;
else if (a->idx > b->idx) return 1;
else return 0;
}
static struct bind_profile *find_bind_profile_by_index(struct socket_enhancer_config *config, uint16_t idx) {
struct bind_profile dummy = {.idx = idx};
return bsearch(&dummy, config->bind_profile_head, config->bind_profile_size, sizeof(struct bind_profile), compare_bind_profiles);
}
static int get_idx_by_address(const struct sockaddr *addr, socklen_t len) {
uint32_t ipv4_address = 0;
if ((len == sizeof(struct sockaddr_in6)) && (addr->sa_family == AF_INET6)) {
const struct sockaddr_in6 *addr6 = (const struct sockaddr_in6 *) addr;
if (IN6_IS_ADDR_V4MAPPED(&addr6->sin6_addr)) {
ipv4_address = ntohl(addr6->sin6_addr.s6_addr32[3]);
goto ipv4;
#if __BYTE_ORDER == __LITTLE_ENDIAN
} else if ((addr6->sin6_addr.s6_addr32[0] == 0x00808ffeU)
#else
} else if ((addr6->sin6_addr.s6_addr32[0] == 0xfe8f8000U)
#endif
&& (addr6->sin6_addr.s6_addr32[1] == 0U) && (addr6->sin6_addr.s6_addr32[2] == 0U) && (addr6->sin6_addr.s6_addr16[6] == 0U)) {
uint16_t idxval_r = ntohs(addr6->sin6_addr.s6_addr16[7]);
if (idxval_r & 0x8000U) {
return idxval_r;
}
} else if (IN6_IS_ADDR_LINKLOCAL(&addr6->sin6_addr)) return 63;
else if (IN6_IS_ADDR_LOOPBACK(&addr6->sin6_addr)) return 61;
else return 60;
} else if ((len == sizeof(struct sockaddr_in)) && (addr->sa_family == AF_INET)) {
const struct sockaddr_in *addr4 = (const struct sockaddr_in *) addr;
ipv4_address = ntohl(addr4->sin_addr.s_addr);
goto ipv4;
}
return -1;
ipv4:
if ((ipv4_address & 0xffffc000U) == 0x7fa74000U) {
return 0x4000U | (ipv4_address & 0x3fffU);
} else if ((ipv4_address & 0xff000000U) == 0x7f000000U) {
return 41;
} else {
return 40;
}
}
static int apply_bind_profile(int socket_fd, uint16_t idx, uint16_t port, struct socket_enhancer_config *config, int do_bind) {
struct bind_profile *profile = find_bind_profile_by_index(config, idx);
if (profile) {
if (handle_bind_profile(socket_fd, profile, do_bind, port, config)) return -1;
return 1;
}
if ((idx >= 16384) && config->has_bp_high) {
errno = EADDRNOTAVAIL;
return -1;
}
return 0;
}
static int apply_bind_profile_sockname(int socket_fd, const struct sockaddr *addr, socklen_t len, struct socket_enhancer_config *config, int do_bind) {
int profile_idx = get_idx_by_address(addr, len);
if (profile_idx < 0) return 0;
if ((len == sizeof(struct sockaddr_in6)) && (addr->sa_family == AF_INET6)) {
return apply_bind_profile(socket_fd, profile_idx, ((struct sockaddr_in6 *) addr)->sin6_port, config, do_bind);
} else if ((len == sizeof(struct sockaddr_in)) && (addr->sa_family == AF_INET)) {
return apply_bind_profile(socket_fd, profile_idx, ((struct sockaddr_in *) addr)->sin_port, config, do_bind);
}
return 0;
}
static int parse_bind_profile_string(const char *input_string, struct bind_profile *result) {
memset(result, 0, sizeof(struct bind_profile));
char *saveptr = NULL;
char *input_string_d = strdup(input_string);
if (!input_string_d) return -1;
char *idx_str = strtok_r(input_string_d, "/", &saveptr);
if (!idx_str) goto out;
unsigned long idx_num = strtoul(idx_str, NULL, 0);
if ((idx_num == 0) || (idx_num > 65535)) goto out;
result->idx = idx_num;
while (1) {
char *token = strtok_r(NULL, "/", &saveptr);
if (!token) break;
switch (token[0]) {
case 'M':
if (result->has_fwmark) goto out;
errno = 0;
unsigned long fwmark = strtoul(&token[1], NULL, 0);
if (errno || (fwmark > 4294967295UL)) goto out;
result->has_fwmark = 1;
result->fwmark = fwmark;
break;
case 'D':
if (result->has_if) goto out;
char *ifname = strdup(&token[1]);
if (!ifname) goto out;
result->bind_interface.ifname = ifname;
result->has_if = 1;
result->has_if_name = 1;
break;
case 'I':
if (result->has_if) goto out;
errno = 0;
unsigned long ifindex = strtoul(&token[1], NULL, 0);
if (errno || (ifindex > 4294967295UL)) goto out;
result->bind_interface.ifindex = ifindex;
result->has_if = 1;
result->has_if_name = 0;
break;
case 'T':
result->set_transparent = 1;
break;
case 'B':
if (result->has_bind_address) goto out;
if (strchr(&token[1], ':')) {
if (inet_pton(AF_INET6, &token[1], &result->bind_address) != 1) goto out;
} else {
result->bind_address.s6_addr32[0] = 0;
result->bind_address.s6_addr32[1] = 0;
result->bind_address.s6_addr16[4] = 0;
result->bind_address.s6_addr16[5] = 0xffffU;
if (inet_pton(AF_INET, &token[1], &result->bind_address.s6_addr32[3]) != 1) goto out;
}
result->has_bind_address = 1;
break;
default:
goto out;
}
}
free(input_string_d);
return 0;
out:
if (result->has_if_name) free(result->bind_interface.ifname);
free(input_string_d);
return -1;
}
static int parse_ipv6_with_scope(char *str, struct ipv6_with_scope *result) {
char *percent_brk = strchr(str, '%');
if (percent_brk) {
char *interface_name = &percent_brk[1];
*percent_brk = 0;
uint32_t index;
if ((interface_name[0] >= '0') && (interface_name[0] <= '9')) {
index = strtoul(interface_name, NULL, 0);
} else {
index = if_nametoindex(interface_name);
/* index = 0 on failure, which fails gracefully */
// if (!index) return -1;
}
struct in6_addr res_addr = {0};
if (inet_pton(AF_INET6, str, &res_addr) != 1) return -1;
result->scope_id = index;
memcpy(&result->address, &res_addr, sizeof(struct in6_addr));
} else {
int results = inet_pton(AF_INET6, str, &result->address);
if (results != 1) return -1;
result->scope_id = 0;
}
return 0;
}
static struct socket_enhancer_config *global_config = NULL;
static void parse_v4(const char *addr, struct in_addr *result) {
if (inet_pton(AF_INET, addr, result) != 1) {
fprintf(stderr, "Invalid IPv4 address %s\n", addr);
abort();
}
}
static void parse_v6(char *addr, struct ipv6_with_scope *result) {
if (parse_ipv6_with_scope(addr, result)) {
fprintf(stderr, "Invalid IPv6 address %s\n", addr);
abort();
}
}
__attribute__((constructor))
static void socket_enhancer_init(void) {
void *real_bind_p = dlsym(RTLD_NEXT, "bind");
if (!real_bind_p) abort();
void *real_connect_p = dlsym(RTLD_NEXT, "connect");
if (!real_connect_p) abort();
void *real_socket_p = dlsym(RTLD_NEXT, "socket");
if (!real_socket_p) abort();
struct socket_enhancer_config *temp_config = calloc(sizeof(struct socket_enhancer_config), 1);
if (!temp_config) abort();
temp_config->real_bind = real_bind_p;
temp_config->real_connect = real_connect_p;
temp_config->real_socket = real_socket_p;
const char *config_str = getenv("SOCKET_ENHANCER_CONFIG");
if (config_str) {
char *dup_configstr = strdup(config_str);
if (!dup_configstr) abort();
char *saveptr = NULL;
for (char *token = strtok_r(dup_configstr, ",", &saveptr); token; token = strtok_r(NULL, ",", &saveptr)) {
if (strnlen(token, 5) < 5) {
fprintf(stderr, "Invalid config option %s\n", token);
abort();
return;
}
if (token[4] != '=') {
fprintf(stderr, "Config option must be name=value\n");
abort();
return;
}
uint32_t option = ntohl(*(uint32_t *) token);
token[4] = 0;
char *value = &token[5];
unsigned long option_numeric_value = 0;
switch (option) {
case 0x69707634: /* "ipv4" */
parse_v4(value, &temp_config->ipv4_default);
temp_config->has_v4_default = 1;
break;
case 0x76346c62: /* "v4lb" */
parse_v4(value, &temp_config->ipv4_loopback);
temp_config->has_v4_loopback = 1;
break;
case 0x69707636: /* "ipv6" */
parse_v6(value, &temp_config->ipv6_default);
temp_config->has_v6_default = 1;
break;
case 0x76366c6c: /* "v6ll" */
parse_v6(value, &temp_config->ipv6_linklocal);
temp_config->has_v6_linklocal = 1;
break;
case 0x76346d36: /* "v4m6" */
parse_v6(value, &temp_config->ipv6_v4mapv6);
temp_config->has_v6_v4mapv6 = 1;
break;
case 0x76367571: /* "v6uq" */
parse_v6(value, &temp_config->ipv6_uniquelocal);
temp_config->has_v6_uniquelocal = 1;
break;
case 0x7636756c: /* "v6ul" */
option_numeric_value = strtoul(value, NULL, 0);
if (option_numeric_value > 3) goto out_of_range;
temp_config->universal_link_local_mode = option_numeric_value;
break;
case 0x66726562: /* "freb" */
option_numeric_value = strtoul(value, NULL, 0);
if (option_numeric_value > 3) goto out_of_range;
temp_config->always_freebind = option_numeric_value;
break;
case 0x62647072: /* "bdpr" */
{
struct bind_profile result = {};
if (parse_bind_profile_string(value, &result)) {
fprintf(stderr, "Invalid bind profile %s\n", value);
abort();
}
size_t newidx = temp_config->bind_profile_size++;
void *new_head = reallocarray(temp_config->bind_profile_head, sizeof(struct bind_profile), newidx+1);
if (!new_head) {
abort();
}
temp_config->bind_profile_head = new_head;
memcpy(&temp_config->bind_profile_head[newidx], &result, sizeof(struct bind_profile));
if (result.idx >= 16384) {
temp_config->has_bp_high = 1;
}
}
break;
default:
fprintf(stderr, "Invalid config option %s\n", token);
abort();
return;
}
continue;
out_of_range:
fprintf(stderr, "Value %lu for %s out of range\n", option_numeric_value, token);
abort();
return;
}
free(dup_configstr);
qsort(temp_config->bind_profile_head, temp_config->bind_profile_size, sizeof(struct bind_profile), compare_bind_profiles);
}
__atomic_store_n(&global_config, temp_config, __ATOMIC_SEQ_CST);
}
static void convert_universal_linklocal(struct sockaddr_in6 *addr) {
if (!addr->sin6_scope_id) {
#if __BYTE_ORDER == __LITTLE_ENDIAN
if (addr->sin6_addr.s6_addr32[0] == 0x000090fe) {
addr->sin6_addr.s6_addr32[0] = 0x000080fe;
#else
if (addr->sin6_addr.s6_addr32[0] == 0xfe900000) {
addr->sin6_addr.s6_addr32[0] = 0xfe800000;
#endif
addr->sin6_scope_id = ntohl(addr->sin6_addr.s6_addr32[1]);
addr->sin6_addr.s6_addr32[1] = 0;
}
}
#if 0
}
#endif
}
static int try_preconnect_bind_v4(int fd, const struct in_addr *bind_addr, int freebind, uint16_t bind_profile_idx, struct socket_enhancer_config *config) {
struct sockaddr_in existing_address = {0};
socklen_t addrlen = sizeof(struct sockaddr_in);
if (getsockname(fd, (struct sockaddr *) &existing_address, &addrlen)) return -1;
if (addrlen == sizeof(struct sockaddr_in)) {
if (existing_address.sin_family == AF_INET) {
if (*(uint32_t *) &existing_address.sin_addr) return 0;
if (apply_bind_profile(fd, bind_profile_idx, 0, config, 0) < 0) return -1;
}
}
if (!bind_addr) return 0;
int one = 1;
setsockopt(fd, SOL_IP, IP_BIND_ADDRESS_NO_PORT, &one, sizeof(one));
one = 1;
if (freebind) setsockopt(fd, SOL_IP, IP_FREEBIND, &one, sizeof(one));
memset(&existing_address, 0, sizeof(existing_address));
existing_address.sin_family = AF_INET;
memcpy(&existing_address.sin_addr, bind_addr, sizeof(struct in_addr));
return config->real_bind(fd, (struct sockaddr *) &existing_address, sizeof(existing_address));
}
static int try_preconnect_bind_v6(int fd, const struct ipv6_with_scope *bind_addr, int freebind, uint16_t bind_profile_idx, struct socket_enhancer_config *config) {
struct sockaddr_in6 existing_address = {0};
socklen_t addrlen = sizeof(struct sockaddr_in6);
if (getsockname(fd, (struct sockaddr *) &existing_address, &addrlen)) return -1;
if (addrlen == sizeof(struct sockaddr_in6)) {
if (existing_address.sin6_family == AF_INET6) {
if (existing_address.sin6_addr.s6_addr32[0]) return 0;
if (existing_address.sin6_addr.s6_addr32[1]) return 0;
if (existing_address.sin6_addr.s6_addr32[2]) return 0;
if (existing_address.sin6_addr.s6_addr32[3]) return 0;
if (apply_bind_profile(fd, bind_profile_idx, 0, config, 0) < 0) return -1;
}
}
if (!bind_addr) return 0;
int one = 1;
setsockopt(fd, SOL_IP, IP_BIND_ADDRESS_NO_PORT, &one, sizeof(one));
one = 1;
if (freebind) setsockopt(fd, SOL_IP, IP_FREEBIND, &one, sizeof(one));
memset(&existing_address, 0, sizeof(existing_address));
existing_address.sin6_family = AF_INET6;
memcpy(&existing_address.sin6_addr, &bind_addr->address, sizeof(struct in6_addr));
existing_address.sin6_scope_id = bind_addr->scope_id;
return config->real_bind(fd, (struct sockaddr *) &existing_address, sizeof(existing_address));
}
int connect(int fd, const struct sockaddr *addr_, socklen_t len_) {
if (!addr_) {
errno = EFAULT;
return -1;
}
const struct sockaddr *addr = addr_;
socklen_t len = len_;
union {
struct sockaddr_in ipv4_addr;
struct sockaddr_in6 ipv6_addr;
} new_addr;
memset(&new_addr, 0, sizeof(new_addr));
struct socket_enhancer_config *config = __atomic_load_n(&global_config, __ATOMIC_SEQ_CST);
if (!config) abort();
int always_freebind = !!(config->always_freebind & 2);
if (len == sizeof(struct sockaddr_in6)) {
if (addr->sa_family == AF_INET6) {
const struct ipv6_with_scope *bind_addr = NULL;
struct ipv6_with_scope tmp_addr = {0};
memcpy(&new_addr.ipv6_addr, addr, sizeof(struct sockaddr_in6));
addr = (struct sockaddr *) &new_addr.ipv6_addr;
int bind_profile_idx = 64;
if (IN6_IS_ADDR_LINKLOCAL(&new_addr.ipv6_addr.sin6_addr)) {
bind_profile_idx = 66;
if (config->universal_link_local_mode & 2) {
convert_universal_linklocal(&new_addr.ipv6_addr);
}
if (config->has_v6_linklocal) {
bind_addr = &config->ipv6_linklocal;
if (IN6_IS_ADDR_UNSPECIFIED(&bind_addr->address)) {
if (!new_addr.ipv6_addr.sin6_scope_id) {
new_addr.ipv6_addr.sin6_scope_id = bind_addr->scope_id;
}
bind_addr = NULL;
}
} else if (config->has_v6_default) {
bind_addr = &config->ipv6_default;
}
} else if (IN6_IS_ADDR_V4MAPPED(&new_addr.ipv6_addr.sin6_addr)) {
bind_profile_idx = 44;
if (config->has_v6_v4mapv6) {
bind_addr = &config->ipv6_v4mapv6;
} else if (config->has_v4_default) {
tmp_addr.address.s6_addr16[4] = 0;
tmp_addr.address.s6_addr16[5] = 0xffff;
tmp_addr.address.s6_addr32[3] = *(uint32_t *) &config->ipv4_default;
bind_addr = &tmp_addr;
}
} else if ((new_addr.ipv6_addr.sin6_addr.s6_addr[0] & 0xfe) == 0xfc) {
bind_profile_idx = 67;
if (config->has_v6_uniquelocal) {
bind_addr = &config->ipv6_uniquelocal;
} else if (config->has_v6_default) {
bind_addr = &config->ipv6_default;
}
} else {
if (config->has_v6_default) {
bind_addr = &config->ipv6_default;
}
}
if (try_preconnect_bind_v6(fd, bind_addr, always_freebind, bind_profile_idx, config)) return -1;
}
} else if (len == sizeof(struct sockaddr_in)) {
if (addr->sa_family == AF_INET) {
memcpy(&new_addr.ipv4_addr, addr, sizeof(struct sockaddr_in));
addr = (struct sockaddr *) &new_addr.ipv4_addr;
struct in_addr *v4_address = &new_addr.ipv4_addr.sin_addr;
if ((ntohl(v4_address->s_addr) & 0xff000000) == 0x7f000000) {
if (try_preconnect_bind_v4(fd, config->has_v4_loopback ? &config->ipv4_loopback : NULL, always_freebind, 45, config)) return -1;
} else {
if (try_preconnect_bind_v4(fd, config->has_v4_default ? &config->ipv4_default : NULL, always_freebind, 44, config)) return -1;
}
}
}
return config->real_connect(fd, addr, len);
}
int bind(int fd, const struct sockaddr *addr_, socklen_t len_) {
if (!addr_) {
errno = EFAULT;
return -1;
}
struct socket_enhancer_config *config = __atomic_load_n(&global_config, __ATOMIC_SEQ_CST);
if (!config) abort();
int always_freebind = !!(config->always_freebind & 1);
const struct sockaddr *addr = addr_;
socklen_t len = len_;
struct sockaddr_in6 ipv6_addr = {0};
if (always_freebind) {
int one = 1;
setsockopt(fd, SOL_IP, IP_FREEBIND, &one, sizeof(one));
}
if (len == sizeof(struct sockaddr_in6)) {
if (addr->sa_family == AF_INET6) {
memcpy(&ipv6_addr, addr, sizeof(struct sockaddr_in6));
addr = (struct sockaddr *) &ipv6_addr;
if (config->universal_link_local_mode & 1) {
convert_universal_linklocal(&ipv6_addr);
}
int r = apply_bind_profile_sockname(fd, (struct sockaddr *) &ipv6_addr, sizeof(struct sockaddr_in6), config, 1);
if (r < 0) {
if (errno == 0) errno = EADDRNOTAVAIL;
return -1;
}
if (r == 1) return 0;
}
} else if ((len == sizeof(struct sockaddr_in)) && (addr->sa_family == AF_INET)) {
struct sockaddr_in ipv4_addr;
memcpy(&ipv4_addr, addr, sizeof(struct sockaddr_in));
int r = apply_bind_profile_sockname(fd, (struct sockaddr *) &ipv4_addr, sizeof(struct sockaddr_in), config, 1);
if (r < 0) {
if (errno == 0) errno = EADDRNOTAVAIL;
return -1;
}
if (r == 1) return 0;
}
return config->real_bind(fd, addr, len);
}
int socket(int domain, int type, int protocol) {
struct socket_enhancer_config *config = __atomic_load_n(&global_config, __ATOMIC_SEQ_CST);
if (!config) abort();
int socket_return = config->real_socket(domain, type, protocol);
if (socket_return < 0) return -1;
switch (domain) {
case AF_INET:
if (apply_bind_profile(socket_return, 4, 0, config, 0) < 0) goto out;
break;
case AF_INET6:
if (apply_bind_profile(socket_return, 6, 0, config, 0) < 0) goto out;
break;
}
return socket_return;
out:
close(socket_return);
return -1;
}
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