Sockets read after a wait are non-blocking, and a read finding nothing waits again

A wait may end with nothing to read: a TLS record not yet whole, a
connection gone before it is accepted, and, once clients share a
thread, nothing more than a chance to try. Where a read or an accept()
followed a wait on a blocking socket, or ended the operation when it
found nothing, the socket is non-blocking and the wait is made again:
the listening sockets of SOCKS BIND and of FTP passive mode, httpsrv
reading what is left of a request body, and the RADIUS client, which
reads with sockrecvfrom().

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/authradius.c

@@ -294,10 +294,8 @@ int radsend(struct clientparam * param, int auth, int stop){
 	int total_length;
 	int len;
 	PROXYSOCKADDRTYPE     saremote;
-	struct pollfd fds[1];
 	char vector[AUTH_VECTOR_LEN];
 	radius_packet_t packet, rpacket;
-	SASIZETYPE salen;
 	int data_len;
 	int count=0;
 	uint8_t *attr;
@@ -545,6 +543,7 @@ int radsend(struct clientparam * param, int auth, int stop){
 			if ((sockfd = so._socket(so.state, SASOCK(&saremote), SOCK_DGRAM, 0)) < 0) {
 			    return 4;
 			}
+			nonblock(sockfd);
 			remsock = sockfd;
 /*
 		}
@@ -557,17 +556,8 @@ int radsend(struct clientparam * param, int auth, int stop){
 			continue;
 		}
 
-	        memset(fds, 0, sizeof(fds));
+		data_len = sockrecvfrom(NULL, remsock, (struct sockaddr *)&saremote, (unsigned char *)&rpacket,
-	        fds[0].fd = remsock;
+			sizeof(packet)-16, param->srv->config->timeouts[SINGLEBYTE_L]*1000);
-	        fds[0].events = POLLIN;
-		if(sockpoll(&so, so.state, fds, 1, param->srv->config->timeouts[SINGLEBYTE_L]*1000) <= 0) {
-			continue;
-		}
-
-		salen = sizeof(saremote);
-				
-		data_len = so._recvfrom(so.state, remsock, (char *)&rpacket, sizeof(packet)-16,
-			0, (struct sockaddr *)&saremote, &salen);
 
 
 		if (data_len < 20) {

src/ftppr.c

@@ -138,6 +138,7 @@ void * ftpprchild(struct clientparam* param) {
 		if(bindwithrange(param, clidatasock, &param->sincl, param->intport)){RETURN(822);}
 		if (pasv) {
 			if(param->srv->so._listen(param->sostate, clidatasock, 1)) {RETURN(823);}
+			nonblock(clidatasock);
 			sasize = sizeof(param->sincl);
 			if(param->srv->so._getsockname(param->sostate, clidatasock, (struct sockaddr *)&param->sincl, &sasize)){RETURN(824);}
 			if(pasv == 1){
@@ -222,12 +223,14 @@ void * ftpprchild(struct clientparam* param) {
 			fds.fd = clidatasock;
 			fds.events = POLLIN;
 
-			res = sockpoll(&param->srv->so, param->sostate, &fds, 1, param->srv->timeouts[STRING_L]*1000);
+			do {
-			if(res != 1) {
+				res = sockpoll(&param->srv->so, param->sostate, &fds, 1, param->srv->timeouts[STRING_L]*1000);
-				RETURN(857);
+				if(res != 1) {
-			}
+					RETURN(857);
-			sasize = sizeof(param->sincr);
+				}
-			ss = param->srv->so._accept(param->sostate, clidatasock, (struct sockaddr *)&param->sincr, &sasize);
+				sasize = sizeof(param->sincr);
+				ss = param->srv->so._accept(param->sostate, clidatasock, (struct sockaddr *)&param->sincr, &sasize);
+			} while (ss == INVALID_SOCKET && acceptagain());
 			if (ss == INVALID_SOCKET) { RETURN (858);}
 #ifdef _WIN32
 			{ unsigned long ul = 1; ioctlsocket(ss, FIONBIO, &ul); }

src/httpsrv.c

@@ -1189,6 +1189,7 @@ static void httpsrv_linger(struct clientparam *param)
 		if(sockpoll(&param->srv->so, param->sostate, &fd, 1, timeo * 1000) <= 0) break;
 		got = (int)param->srv->so._recv(param->sostate, param->clisock, buf,
 			(left > HTTPSRV_BLOCK)? (int)HTTPSRV_BLOCK : (int)left, 0);
+		if(got < 0 && (errno == EAGAIN || errno == EINTR)) continue;
 		if(got <= 0) break;
 		left -= (uint64_t)got;
 	}

src/socks.c

@@ -351,17 +351,21 @@ fflush(stderr);
 				break;
 			case 2:
 				param->srv->so._listen (param->sostate, param->remsock, 1);
+				nonblock(param->remsock);
 				
 				fds[0].fd = param->remsock;
 				fds[1].fd = param->clisock;
 				fds[0].events = fds[1].events = POLLIN;
-				res = sockpoll(&param->srv->so, param->sostate, fds, 2, param->srv->timeouts[CONNECTION_L] * 1000);
+				do {
+					res = sockpoll(&param->srv->so, param->sostate, fds, 2, param->srv->timeouts[CONNECTION_L] * 1000);
+					if (res < 1 || fds[1].revents) break;
+					sasize = sizeof(param->sinsr);
+					s = param->srv->so._accept(param->sostate, param->remsock, (struct sockaddr *)&param->sinsr, &sasize);
+				} while (s == INVALID_SOCKET && acceptagain());
 				if (res < 1 || fds[1].revents) {
 					res = 460;
 					break;
 				}
-				sasize = sizeof(param->sinsr);
-				s = param->srv->so._accept(param->sostate, param->remsock, (struct sockaddr *)&param->sinsr, &sasize);
 				param->srv->so._closesocket(param->sostate, param->remsock);
 				param->remsock = s;
 				if(s == INVALID_SOCKET) {