diff --git a/desync.c b/desync.c
index 4bb3819..4fe70f7 100644
--- a/desync.c
+++ b/desync.c
@@ -47,7 +47,7 @@ int setttl(int fd, int ttl)
 }
 
 #ifdef __linux__
-int drop_sack(int fd)
+static int drop_sack(int fd)
 {
     struct sock_filter code[] = {
         { 0x30, 0, 0, 0x0000000c },
@@ -85,7 +85,7 @@ static inline void delay(long ms)
 #endif
 
 #ifdef __linux__
-void wait_send(int sfd)
+static void wait_send(int sfd)
 {
     for (int i = 0; params.wait_send && i < 500; i++) {
         struct tcp_info tcpi = {};
@@ -122,7 +122,7 @@ void wait_send(int sfd)
 #endif
 
 #ifdef __linux__
-ssize_t send_fake(int sfd, char *buffer,
+static ssize_t send_fake(int sfd, const char *buffer,
         int cnt, long pos, struct desync_params *opt)
 {
     struct sockaddr_in6 addr = {};
@@ -234,7 +234,7 @@ ssize_t send_fake(int sfd, char *buffer,
 #ifdef _WIN32
 OVERLAPPED ov = {};
 
-ssize_t send_fake(int sfd, char *buffer,
+static ssize_t send_fake(int sfd, const char *buffer,
         int cnt, long pos, struct desync_params *opt)
 {
     struct packet pkt;
@@ -334,8 +334,8 @@ ssize_t send_fake(int sfd, char *buffer,
 }
 #endif
 
-ssize_t send_oob(int sfd, char *buffer,
-        ssize_t n, long pos, char *c)
+static ssize_t send_oob(int sfd, char *buffer,
+        ssize_t n, long pos, const char *c)
 {
     char rchar = buffer[pos];
     buffer[pos] = c[1] ? c[0] : 'a';
@@ -357,8 +357,8 @@ ssize_t send_oob(int sfd, char *buffer,
 }
 
 
-ssize_t send_disorder(int sfd, 
-        char *buffer, long pos)
+static ssize_t send_disorder(int sfd, 
+        const char *buffer, long pos)
 {
     int bttl = 1;
     
@@ -378,8 +378,8 @@ ssize_t send_disorder(int sfd,
 }
 
 
-ssize_t send_late_oob(int sfd, char *buffer,
-        ssize_t n, long pos, char *c)
+static ssize_t send_late_oob(int sfd, char *buffer,
+        ssize_t n, long pos, const char *c)
 {
     int bttl = 1;
     
@@ -427,7 +427,7 @@ static long gen_offset(long pos, int flag,
 
 
 ssize_t desync(int sfd, char *buffer, size_t bfsize,
-        ssize_t n, ssize_t offset, struct sockaddr *dst, int dp_c)
+        ssize_t n, ssize_t offset, const struct sockaddr *dst, int dp_c)
 {
     struct desync_params dp = params.dp[dp_c];
     
@@ -599,7 +599,7 @@ int post_desync(int sfd, int dp_c)
 
 
 ssize_t desync_udp(int sfd, char *buffer, size_t bfsize,
-        ssize_t n, struct sockaddr *dst, int dp_c)
+        ssize_t n, const struct sockaddr *dst, int dp_c)
 {
     struct desync_params *dp = &params.dp[dp_c];
     
diff --git a/desync.h b/desync.h
index 2686d96..e33c48e 100644
--- a/desync.h
+++ b/desync.h
@@ -10,9 +10,9 @@
     #include <sys/socket.h>
 #endif
 
-ssize_t desync(int sfd, char *buffer, size_t bfsize, ssize_t n, ssize_t offset, struct sockaddr *dst, int dp_c);
+ssize_t desync(int sfd, char *buffer, size_t bfsize, ssize_t n, ssize_t offset, const struct sockaddr *dst, int dp_c);
 
-ssize_t desync_udp(int sfd, char *buffer, size_t bfsize, ssize_t n, struct sockaddr *dst, int dp_c);
+ssize_t desync_udp(int sfd, char *buffer, size_t bfsize, ssize_t n, const struct sockaddr *dst, int dp_c);
 
 int setttl(int fd, int ttl);
 
diff --git a/extend.c b/extend.c
index c588103..b23da79 100644
--- a/extend.c
+++ b/extend.c
@@ -72,7 +72,7 @@ static ssize_t serialize_addr(const struct sockaddr_ina *dst,
 }
 
 
-static int cache_get(struct sockaddr_ina *dst)
+static int cache_get(const struct sockaddr_ina *dst)
 {
     uint8_t key[KEY_SIZE] = { 0 };
     int len = serialize_addr(dst, key, sizeof(key));
@@ -90,7 +90,7 @@ static int cache_get(struct sockaddr_ina *dst)
 }
 
 
-static int cache_add(struct sockaddr_ina *dst, int m)
+static int cache_add(const struct sockaddr_ina *dst, int m)
 {
     assert(m >= 0 && m < params.dp_count);
     
@@ -117,7 +117,7 @@ static int cache_add(struct sockaddr_ina *dst, int m)
 }
 
 
-static inline bool check_port(uint16_t *p, struct sockaddr_in6 *dst)
+static inline bool check_port(const uint16_t *p, const struct sockaddr_in6 *dst)
 {
     return (dst->sin6_port >= p[0] 
             && dst->sin6_port <= p[1]);
@@ -125,7 +125,7 @@ static inline bool check_port(uint16_t *p, struct sockaddr_in6 *dst)
 
 
 int connect_hook(struct poolhd *pool, struct eval *val, 
-        struct sockaddr_ina *dst, int next)
+        const struct sockaddr_ina *dst, int next)
 {
     int m = cache_get(dst);
     val->cache = (m == 0);
@@ -135,7 +135,7 @@ int connect_hook(struct poolhd *pool, struct eval *val,
 }
 
 
-int socket_mod(int fd, struct sockaddr *dst)
+int socket_mod(int fd)
 {
     if (params.custom_ttl) {
         if (setttl(fd, params.def_ttl) < 0) {
@@ -171,7 +171,8 @@ static int reconnect(struct poolhd *pool, struct eval *val, int m)
 }
 
 
-static bool check_host(struct mphdr *hosts, char *buffer, ssize_t n)
+static bool check_host(
+        struct mphdr *hosts, const char *buffer, ssize_t n)
 {
     char *host = 0;
     int len;
@@ -195,7 +196,7 @@ static bool check_host(struct mphdr *hosts, char *buffer, ssize_t n)
 }
 
 
-static bool check_proto_tcp(int proto, char *buffer, ssize_t n)
+static bool check_proto_tcp(int proto, const char *buffer, ssize_t n)
 {
     if (proto & IS_TCP) {
         return 1;
@@ -212,7 +213,7 @@ static bool check_proto_tcp(int proto, char *buffer, ssize_t n)
 }
 
 
-static bool check_round(int *nr, int r)
+static bool check_round(const int *nr, int r)
 {
     return (!nr[1] && r <= 1) || (r >= nr[0] && r <= nr[1]);
 }
@@ -279,7 +280,7 @@ static int on_fin(struct poolhd *pool, struct eval *val)
 
 
 static int on_response(struct poolhd *pool, struct eval *val, 
-        char *resp, ssize_t sn)
+        const char *resp, ssize_t sn)
 {
     int m = val->pair->attempt + 1;
     
@@ -318,7 +319,7 @@ static inline void free_first_req(struct eval *client)
 }
 
 
-static int setup_conn(struct eval *client, char *buffer, ssize_t n)
+static int setup_conn(struct eval *client, const char *buffer, ssize_t n)
 {
     int m = client->attempt;
     
@@ -361,7 +362,7 @@ static int cancel_setup(struct eval *remote)
 }
 
 
-int send_saved_req(struct poolhd *pool,
+static int send_saved_req(struct poolhd *pool,
         struct eval *client, char *buffer, ssize_t bfsize)
 {
     ssize_t offset = client->buff.offset;
@@ -547,7 +548,7 @@ ssize_t udp_hook(struct eval *val,
 
 
 #ifdef __linux__
-int protect(int conn_fd, const char *path)
+static int protect(int conn_fd, const char *path)
 {
     struct sockaddr_un sa;
     sa.sun_family = AF_UNIX;
diff --git a/extend.h b/extend.h
index affce4f..edae150 100644
--- a/extend.h
+++ b/extend.h
@@ -5,10 +5,10 @@
 
 #include "proxy.h"
 
-int socket_mod(int fd, struct sockaddr *dst);
+int socket_mod(int fd);
 
 int connect_hook(struct poolhd *pool, struct eval *val, 
-        struct sockaddr_ina *dst, int next);
+        const struct sockaddr_ina *dst, int next);
         
 ssize_t tcp_send_hook(struct eval *val,
         char *buffer, size_t bfsize, ssize_t n);
@@ -23,7 +23,7 @@ int on_first_tunnel(struct poolhd *pool,
         struct eval *val, char *buffer, ssize_t bfsize, int etype);
         
 #ifdef __linux__
-int protect(int conn_fd, const char *path);
+static int protect(int conn_fd, const char *path);
 #else
 #define protect(fd, path) 0
 #endif
diff --git a/main.c b/main.c
index 810e1f3..c0cefdc 100644
--- a/main.c
+++ b/main.c
@@ -59,7 +59,7 @@ struct params params = {
 };
 
 
-const char help_text[] = {
+const static char help_text[] = {
     "    -i, --ip, <ip>            Listening IP, default 0.0.0.0\n"
     "    -p, --port <num>          Listening port, default 1080\n"
     #ifdef __linux__
diff --git a/packets.c b/packets.c
index 3e04482..60ec768 100644
--- a/packets.c
+++ b/packets.c
@@ -60,9 +60,9 @@ char http_data[43] = {
 char udp_data[64] = { 0 };
 
 
-char *strncasestr(char *a, size_t as, char *b, size_t bs)
+static const char *strncasestr(const char *a, size_t as, const char *b, size_t bs)
 {
-    for (char *p = a; ; p++) {
+    for (const char *p = a; ; p++) {
         p = memchr(p, *b, as - (p - a));
         if (!p) {
             return 0;
@@ -78,8 +78,8 @@ char *strncasestr(char *a, size_t as, char *b, size_t bs)
 }
 
 
-size_t find_tls_ext_offset(uint16_t type, 
-        char *data, size_t size, size_t skip) 
+static size_t find_tls_ext_offset(uint16_t type, 
+        const char *data, size_t size, size_t skip) 
 {
     if (size <= (skip + 2)) {
         return 0;
@@ -102,7 +102,7 @@ size_t find_tls_ext_offset(uint16_t type,
 }
 
 
-size_t chello_ext_offset(uint16_t type, char *data, size_t size)
+static size_t chello_ext_offset(uint16_t type, const char *data, size_t size)
 {
     if (size < 44) {
         return 0;
@@ -155,7 +155,7 @@ int change_tls_sni(const char *host, char *buffer, size_t bsize)
 }
 
 
-bool is_tls_chello(char *buffer, size_t bsize)
+bool is_tls_chello(const char *buffer, size_t bsize)
 {
     return (bsize > 5 &&
         ANTOHS(buffer, 0) == 0x1603 &&
@@ -163,7 +163,7 @@ bool is_tls_chello(char *buffer, size_t bsize)
 }
 
 
-int parse_tls(char *buffer, size_t bsize, char **hs)
+int parse_tls(const char *buffer, size_t bsize, char **hs)
 {
     if (!is_tls_chello(buffer, bsize)) {
         return 0;
@@ -178,12 +178,12 @@ int parse_tls(char *buffer, size_t bsize, char **hs)
     if ((sni_offs + 9 + len) > bsize) {
         return 0;
     }
-    *hs = &buffer[sni_offs + 9];
+    *hs = (char *)&buffer[sni_offs + 9];
     return len;
 }
 
 
-bool is_http(char *buffer, size_t bsize)
+bool is_http(const char *buffer, size_t bsize)
 {
     if (bsize < 16 || *buffer > 'T' || *buffer < 'C') {
         return 0;
@@ -201,10 +201,10 @@ bool is_http(char *buffer, size_t bsize)
 }
 
     
-int parse_http(char *buffer, size_t bsize, char **hs, uint16_t *port)
+int parse_http(const char *buffer, size_t bsize, char **hs, uint16_t *port)
 {
-    char *host = buffer, *h_end;
-    char *buff_end = buffer + bsize;
+    const char *host = buffer, *h_end;
+    const char *buff_end = buffer + bsize;
     
     if (!is_http(buffer, bsize)) {
         return 0;
@@ -218,7 +218,7 @@ int parse_http(char *buffer, size_t bsize, char **hs, uint16_t *port)
     while ((buff_end - host) > 0 && isblank((unsigned char) *host)) {
         host++;
     }
-    char *l_end = memchr(host, '\n', buff_end - host);
+    const char *l_end = memchr(host, '\n', buff_end - host);
     if (!l_end) {
         return 0;
     }
@@ -227,7 +227,7 @@ int parse_http(char *buffer, size_t bsize, char **hs, uint16_t *port)
     if (!(isdigit((unsigned char) *(l_end - 1))))
         h_end = 0;
     else {
-        char *h = host;
+        const char *h = host;
         h_end = 0;
         do {
             h = memchr(h, ':', l_end - h);
@@ -249,12 +249,12 @@ int parse_http(char *buffer, size_t bsize, char **hs, uint16_t *port)
             return 0;
         *port = i;
     }
-    *hs = host;
+    *hs = (char *)host;
     return h_end - host;
 }
 
 
-int get_http_code(char *b, size_t n)
+static int get_http_code(const char *b, size_t n)
 {
     if (n < 13) return 0;
     if (strncmp(b, "HTTP/1.", 7)) {
@@ -272,7 +272,8 @@ int get_http_code(char *b, size_t n)
 }
 
 
-bool is_http_redirect(char *req, size_t qn, char *resp, size_t sn)
+bool is_http_redirect(
+        const char *req, size_t qn, const char *resp, size_t sn)
 {
     char *host = 0;
     int len = parse_http(req, qn, &host, 0);
@@ -284,7 +285,7 @@ bool is_http_redirect(char *req, size_t qn, char *resp, size_t sn)
     if (code > 308 || code < 300) {
         return 0;
     }
-    char *location = strncasestr(resp, sn, "\nLocation:", 10);
+    const char *location = strncasestr(resp, sn, "\nLocation:", 10);
     if (!location) {
         return 0;
     }
@@ -329,7 +330,7 @@ bool is_http_redirect(char *req, size_t qn, char *resp, size_t sn)
 }
 
 
-bool neq_tls_sid(char *req, size_t qn, char *resp, size_t sn)
+bool neq_tls_sid(const char *req, size_t qn, const char *resp, size_t sn)
 {
     if (qn < 75 || sn < 75) {
         return 0;
@@ -351,7 +352,7 @@ bool neq_tls_sid(char *req, size_t qn, char *resp, size_t sn)
 }
 
 
-bool is_tls_shello(char *buffer, size_t bsize)
+bool is_tls_shello(const char *buffer, size_t bsize)
 {
     return (bsize > 5 &&
         ANTOHS(buffer, 0) == 0x1603 &&
diff --git a/packets.h b/packets.h
index 0fb7d85..e2ddb42 100644
--- a/packets.h
+++ b/packets.h
@@ -23,23 +23,21 @@ extern char udp_data[64];
 
 int change_tls_sni(const char *host, char *buffer, size_t bsize);
 
-bool is_tls_chello(char *buffer, size_t bsize);
+bool is_tls_chello(const char *buffer, size_t bsize);
 
-int parse_tls(char *buffer, size_t bsize, char **hs);
+int parse_tls(const char *buffer, size_t bsize, char **hs);
 
-bool is_http(char *buffer, size_t bsize);
+bool is_http(const char *buffer, size_t bsize);
 
-int parse_http(char *buffer, size_t bsize, char **hs, uint16_t *port);
+int parse_http(const char *buffer, size_t bsize, char **hs, uint16_t *port);
 
 int mod_http(char *buffer, size_t bsize, int m);
 
-int get_http_code(char *b, size_t n);
+bool is_http_redirect(const char *req, size_t qn, const char *resp, size_t sn);
 
-bool is_http_redirect(char *req, size_t qn, char *resp, size_t sn);
+bool neq_tls_sid(const char *req, size_t qn, const char *resp, size_t sn);
 
-bool neq_tls_sid(char *req, size_t qn, char *resp, size_t sn);
-
-bool is_tls_shello(char *buffer, size_t bsize);
+bool is_tls_shello(const char *buffer, size_t bsize);
 
 int part_tls(char *buffer, size_t bsize, ssize_t n, long pos);
 
diff --git a/proxy.c b/proxy.c
index 286e314..4f68eef 100644
--- a/proxy.c
+++ b/proxy.c
@@ -75,7 +75,7 @@ void map_fix(struct sockaddr_ina *addr, char f6)
 
 
 static inline char addr_equ(
-        struct sockaddr_ina *a, struct sockaddr_ina *b)
+        const struct sockaddr_ina *a, const struct sockaddr_ina *b)
 {
     if (a->sa.sa_family == AF_INET) {
         return 
@@ -121,7 +121,7 @@ static inline int nb_socket(int domain, int type)
 }
 
 
-int resolve(char *host, int len, 
+static int resolve(char *host, int len, 
         struct sockaddr_ina *addr, int type) 
 {
     struct addrinfo hints = {0}, *res = 0;
@@ -149,7 +149,7 @@ int resolve(char *host, int len,
 }
 
 
-int auth_socks5(int fd, char *buffer, ssize_t n)
+static int auth_socks5(int fd, const char *buffer, ssize_t n)
 {
     if (n <= 2 || (uint8_t)buffer[1] != (n - 2)) {
         return -1;
@@ -160,8 +160,8 @@ int auth_socks5(int fd, char *buffer, ssize_t n)
             c = S_AUTH_NONE;
             break;
         }
-    buffer[1] = c;
-    if (send(fd, buffer, 2, 0) < 0) {
+    uint8_t a[2] = { S_VER5, c };
+    if (send(fd, a, sizeof(a), 0) < 0) {
         uniperror("send");
         return -1;
     }
@@ -169,7 +169,7 @@ int auth_socks5(int fd, char *buffer, ssize_t n)
 }
 
 
-int resp_s5_error(int fd, int e)
+static int resp_s5_error(int fd, int e)
 {
     struct s5_rep s5r = { 
         .ver = 0x05, .code = (uint8_t )e, 
@@ -179,7 +179,7 @@ int resp_s5_error(int fd, int e)
 }
 
 
-int resp_error(int fd, int e, int flag)
+static int resp_error(int fd, int e, int flag)
 {
     if (flag == FLAG_S4) {
         struct s4_req s4r = { 
@@ -220,8 +220,8 @@ int resp_error(int fd, int e, int flag)
 }
 
 
-int s4_get_addr(char *buff, size_t n,
-        struct sockaddr_ina *dst)
+static int s4_get_addr(const char *buff, 
+        size_t n, struct sockaddr_ina *dst)
 {
     if (n < sizeof(struct s4_req) + 1) {
         return -1;
@@ -257,8 +257,8 @@ int s4_get_addr(char *buff, size_t n,
 }
 
 
-int s5_get_addr(char *buffer, size_t n,
-        struct sockaddr_ina *addr, int type) 
+static int s5_get_addr(const char *buffer, 
+        size_t n, struct sockaddr_ina *addr, int type) 
 {
     if (n < S_SIZE_MIN) {
         LOG(LOG_E, "ss: request too small\n");
@@ -303,8 +303,8 @@ int s5_get_addr(char *buffer, size_t n,
 }
 
 
-int s5_set_addr(char *buffer, size_t n,
-        struct sockaddr_ina *addr, char end)
+static int s5_set_addr(char *buffer, size_t n,
+        const struct sockaddr_ina *addr, char end)
 {
     struct s5_req *r = (struct s5_req *)buffer;
     if (n < S_SIZE_I4) {
@@ -350,7 +350,7 @@ static int remote_sock(struct sockaddr_ina *dst, int type)
         uniperror("socket");  
         return -1;
     }
-    if (socket_mod(sfd, &dst->sa) < 0) {
+    if (socket_mod(sfd) < 0) {
         close(sfd);
         return -1;
     }
@@ -374,7 +374,7 @@ static int remote_sock(struct sockaddr_ina *dst, int type)
 
 
 int create_conn(struct poolhd *pool,
-        struct eval *val, struct sockaddr_ina *dst, int next)
+        struct eval *val, const struct sockaddr_ina *dst, int next)
 {
     struct sockaddr_ina addr = *dst;
     
@@ -444,8 +444,8 @@ int create_conn(struct poolhd *pool,
 }
 
 
-int udp_associate(struct poolhd *pool, 
-        struct eval *val, struct sockaddr_ina *dst)
+static int udp_associate(struct poolhd *pool, 
+        struct eval *val, const struct sockaddr_ina *dst)
 {
     struct sockaddr_ina addr = *dst;
     
@@ -563,7 +563,7 @@ static inline int transp_conn(struct poolhd *pool, struct eval *val)
 }
 #endif
 
-static inline int on_accept(struct poolhd *pool, struct eval *val)
+static int on_accept(struct poolhd *pool, const struct eval *val)
 {
     struct sockaddr_ina client;
     struct eval *rval;
@@ -619,7 +619,7 @@ static inline int on_accept(struct poolhd *pool, struct eval *val)
 }
 
 
-int on_tunnel(struct poolhd *pool, struct eval *val, 
+static int on_tunnel(struct poolhd *pool, struct eval *val, 
         char *buffer, size_t bfsize, int etype)
 {
     ssize_t n = 0;
@@ -694,7 +694,7 @@ int on_tunnel(struct poolhd *pool, struct eval *val,
 }
 
 
-int on_udp_tunnel(struct eval *val, char *buffer, size_t bfsize)
+static int on_udp_tunnel(struct eval *val, char *buffer, size_t bfsize)
 {
     char *data = buffer;
     size_t data_len = bfsize;
@@ -887,7 +887,7 @@ static inline int on_connect(struct poolhd *pool, struct eval *val, int e)
 }
 
 
-void close_conn(struct poolhd *pool, struct eval *val)
+static void close_conn(struct poolhd *pool, struct eval *val)
 {
     struct eval *cval = val;
     do {
@@ -986,7 +986,7 @@ int event_loop(int srvfd)
 }
 
 
-int listen_socket(struct sockaddr_ina *srv)
+int listen_socket(const struct sockaddr_ina *srv)
 {
     int srvfd = nb_socket(srv->sa.sa_family, SOCK_STREAM);
     if (srvfd < 0) {
@@ -1014,7 +1014,7 @@ int listen_socket(struct sockaddr_ina *srv)
 }
 
 
-int run(struct sockaddr_ina *srv)
+int run(const struct sockaddr_ina *srv)
 {
     #ifdef SIGPIPE
     if (signal(SIGPIPE, SIG_IGN) == SIG_ERR)
diff --git a/proxy.h b/proxy.h
index 29eaee2..fb28035 100644
--- a/proxy.h
+++ b/proxy.h
@@ -106,18 +106,13 @@ enum s4_rep {
 
 void map_fix(struct sockaddr_ina *addr, char f6);
 
-int resp_error(int fd, int e, int flag);
-
 int create_conn(struct poolhd *pool,
-        struct eval *val, struct sockaddr_ina *dst, int next);
-
-int on_tunnel(struct poolhd *pool, struct eval *val, 
-        char *buffer, size_t bfsize, int out);
-        
-int listen_socket(struct sockaddr_ina *srv);
+        struct eval *val, const struct sockaddr_ina *dst, int next);
+ 
+int listen_socket(const struct sockaddr_ina *srv);
 
 int event_loop(int srvfd);
 
-int run(struct sockaddr_ina *srv);
+int run(const struct sockaddr_ina *srv);
 
 #endif