try fix #122 #123 #124 issues

dnl.c

@@ -490,7 +490,7 @@ static void do_debug(u32 gfw_addr0, u32 gfw_n, u32 chn_addr0, u32 chn_n) {
         }
     }
 
-    /* check map2 hash collisions  */
+    /* check map2 hash collisions */
     if (!map_is_null(&s_map2)) {
         int maxlen = 0;
         for (u32 idx = 0, n = map_cap(&s_map2); idx < n; ++idx) {
@@ -579,8 +579,8 @@ u8 get_name_tag(const char *noalias name, int namelen) {
     assert(n > 0);
 
     u8 name_tag;
-    for (int i = 0; i < n; ++i) {
-        if (exists_in_dnl(sub_names[i], sub_namelens[i], &name_tag))
+    while (--n >= 0) {
+        if (exists_in_dnl(sub_names[n], sub_namelens[n], &name_tag))
             return name_tag;
     }
 

ipset.c

@@ -466,7 +466,7 @@ void ipset_init(void) {
 static inline int send_req(int n_msg) {
     assert(n_msg > 0);
     assert(n_msg <= MSG_N);
-    int n_sent = sendall(sendmmsg, s_sock, s_msgv, n_msg, 0);
+    int n_sent = sendall(x_sendmmsg, s_sock, s_msgv, n_msg, 0);
     assert(n_sent != 0);
     unlikely_if (n_sent != n_msg)
         log_error("failed to send nlmsg: %d != %d, (%d) %s", n_sent, n_msg, errno, strerror(errno));
@@ -477,7 +477,7 @@ static inline int send_req(int n_msg) {
 static inline int recv_res(int n_msg, bool err_if_nomsg) {
     assert(n_msg > 0);
     assert(n_msg <= MSG_N);
-    int n_recv = recvmmsg(s_sock, s_msgv, n_msg, MSG_DONTWAIT, NULL);
+    int n_recv = x_recvmmsg(s_sock, s_msgv, n_msg, MSG_DONTWAIT, NULL);
     assert(n_recv != 0);
     if (n_recv < 0) { /* no-msg or error */
         if (errno == EAGAIN || errno == EWOULDBLOCK)

main.c

@@ -161,7 +161,7 @@ static void handle_local_packet(void) {
 
         log_verbose("forward [%s] to %s (%s)", s_name_buf, g_upstream_addrs[i], is_chinadns_idx(i) ? "chinadns" : "trustdns");
 
-        int n_sent = sendmmsg(s_upstream_sockfds[i], msgv, msg_n, 0);
+        int n_sent = x_sendmmsg(s_upstream_sockfds[i], msgv, msg_n, 0);
         unlikely_if (n_sent != msg_n) {
             if (n_sent < 0)
                 log_error("failed to send query to %s: (%d) %s", g_upstream_addrs[i], errno, strerror(errno));
@@ -325,7 +325,7 @@ static void handle_remote_packet(int index) {
 }
 
 static void handle_timeout_event(struct queryctx *context) {
-    log_warning("upstream reply timeout, unique msgid: %u", (uint)context->unique_msgid);
+    log_verbose("upstream reply timeout, unique msgid: %u", (uint)context->unique_msgid);
     free_context(context);
 }
 
@@ -334,6 +334,8 @@ int main(int argc, char *argv[]) {
     setvbuf(stdout, NULL, _IOLBF, 256);
     opt_parse(argc, argv);
 
+    net_init();
+
     log_info("local listen addr: %s#%u", g_bind_ip, (uint)g_bind_port);
 
     if (g_upstream_addrs[CHINADNS1_IDX]) log_info("chinadns server#1: %s", g_upstream_addrs[CHINADNS1_IDX]);

net.c

@@ -1,6 +1,7 @@
 #define _GNU_SOURCE
 #include "net.h"
 #include "log.h"
+#include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
 #include <errno.h>
@@ -11,6 +12,78 @@
   #define SO_REUSEPORT 15
 #endif
 
+int (*x_recvmmsg)(int sockfd, struct mmsghdr *msgvec, unsigned int vlen, int flags, struct timespec *timeout);
+
+int (*x_sendmmsg)(int sockfd, struct mmsghdr *msgvec, unsigned int vlen, int flags);
+
+static int my_recvmmsg(int sockfd, struct mmsghdr *msgvec, unsigned int vlen, int flags, struct timespec *timeout) {
+    unlikely_if (vlen <= 0 || timeout) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    bool wait_for_one = flags & MSG_WAITFORONE;
+    flags &= ~MSG_WAITFORONE;
+
+    int nrecv = 0;
+
+    for (uint i = 0; i < vlen; ++i) {
+        ssize_t res = recvmsg(sockfd, &msgvec[i].msg_hdr, flags);
+        if (res < 0) break;
+
+        msgvec[i].msg_len = res;
+        ++nrecv;
+
+        if (wait_for_one)
+            flags |= MSG_DONTWAIT;
+    }
+
+    return nrecv ?: -1;
+}
+
+static int my_sendmmsg(int sockfd, struct mmsghdr *msgvec, unsigned int vlen, int flags) {
+    unlikely_if (vlen <= 0) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    int nsent = 0;
+
+    for (uint i = 0; i < vlen; ++i) {
+        ssize_t res = sendmsg(sockfd, &msgvec[i].msg_hdr, flags);
+        if (res < 0) break;
+
+        msgvec[i].msg_len = res;
+        ++nsent;
+    }
+
+    return nsent ?: -1;
+}
+
+void net_init(void) {
+    int res = recvmmsg(-1, NULL, 0, 0, NULL);
+    assert(res == -1);
+    (void)res;
+
+    if (errno != ENOSYS) {
+        x_recvmmsg = recvmmsg;
+    } else {
+        log_info("recvmmsg not implemented, use recvmsg to simulate");
+        x_recvmmsg = my_recvmmsg;
+    }
+
+    res = sendmmsg(-1, NULL, 0, 0);
+    assert(res == -1);
+    (void)res;
+
+    if (errno != ENOSYS) {
+        x_sendmmsg = sendmmsg;
+    } else {
+        log_info("sendmmsg not implemented, use sendmsg to simulate");
+        x_sendmmsg = my_sendmmsg;
+    }
+}
+
 /* setsockopt(IPV6_V6ONLY) */
 static inline void set_ipv6_only(int sockfd) {
     unlikely_if (setsockopt(sockfd, IPPROTO_IPV6, IPV6_V6ONLY, &(int){1}, sizeof(int))) {

net.h

@@ -26,6 +26,14 @@ union skaddr {
 #define skaddr_is_sin6(p) (skaddr_family(p) == AF_INET6)
 #define skaddr_size(p) (skaddr_is_sin(p) ? sizeof((p)->sin) : sizeof((p)->sin6))
 
+/* compatible with old kernel (runtime) */
+extern int (*x_recvmmsg)(int sockfd, struct mmsghdr *msgvec, unsigned int vlen, int flags, struct timespec *timeout);
+
+/* compatible with old kernel (runtime) */
+extern int (*x_sendmmsg)(int sockfd, struct mmsghdr *msgvec, unsigned int vlen, int flags);
+
+void net_init(void);
+
 void set_reuse_port(int sockfd);
 
 int new_udp_socket(int family);