BUG/MINOR: config: Fix setting of alt_proto

This patch fixes the bug presented in issue #3254
(https://github.com/haproxy/haproxy/issues/3254), which
occured on FreeBSD when using a stream socket for in
nameserver section. This bug occured due to an incorrect
reset of the alt_proto for a stream socket when the default
socket is created as a datagram socket. This patch fixes
this bug by doing a late assignment to alt_proto when
a datagram socket is requested, leaving only the modification
of alt_proto done by mptcp. Additional documentation
for the use of alt_proto has also been added to
clarify the use of the alt_proto variable.

diff --git a/src/tools.c b/src/tools.c
index 9a4e1bf6885d1aabc9862c6a3e5bc5736d8fd724..cdbf7e20101fecae607711b54933a85f52c60a78 100644 (file)
--- a/src/tools.c
+++ b/src/tools.c
@@ -987,6 +987,11 @@ struct sockaddr_storage *str2sa_range(const char *str, int *port, int *low, int
        int new_fd = -1;
        enum proto_type proto_type = 0; // to shut gcc warning
        int ctrl_type = 0; // to shut gcc warning
+       /*
+        * Indicates that we want to use an alternate protocol instead of the
+        * default one.
+        * Currently, only MPTCP is defined as an alternate protocol for TCP
+        */
        int alt_proto = 0;
 
        portl = porth = porta = 0;
@@ -1011,7 +1016,6 @@ struct sockaddr_storage *str2sa_range(const char *str, int *port, int *low, int
            ((opts & (PA_O_STREAM|PA_O_DGRAM)) == (PA_O_DGRAM|PA_O_STREAM) && (opts & PA_O_DEFAULT_DGRAM))) {
                proto_type = PROTO_TYPE_DGRAM;
                ctrl_type = SOCK_DGRAM;
-               alt_proto = 1;
        } else {
                proto_type = PROTO_TYPE_STREAM;
                ctrl_type = SOCK_STREAM;
@@ -1026,7 +1030,6 @@ struct sockaddr_storage *str2sa_range(const char *str, int *port, int *low, int
                str2 += 6;
                proto_type = PROTO_TYPE_DGRAM;
                ctrl_type = SOCK_DGRAM;
-               alt_proto = 1;
        }
        else if (strncmp(str2, "quic+", 5) == 0) {
                str2 += 5;
@@ -1043,7 +1046,6 @@ struct sockaddr_storage *str2sa_range(const char *str, int *port, int *low, int
                ss.ss_family = AF_UNIX;
                proto_type = PROTO_TYPE_DGRAM;
                ctrl_type = SOCK_DGRAM;
-               alt_proto = 1;
        }
        else if (strncmp(str2, "uxst@", 5) == 0) {
                str2 += 5;
@@ -1089,7 +1091,6 @@ struct sockaddr_storage *str2sa_range(const char *str, int *port, int *low, int
                ss.ss_family = AF_INET;
                proto_type = PROTO_TYPE_DGRAM;
                ctrl_type = SOCK_DGRAM;
-               alt_proto = 1;
        }
        else if (strncmp(str2, "tcp6@", 5) == 0) {
                str2 += 5;
@@ -1109,7 +1110,6 @@ struct sockaddr_storage *str2sa_range(const char *str, int *port, int *low, int
                ss.ss_family = AF_INET6;
                proto_type = PROTO_TYPE_DGRAM;
                ctrl_type = SOCK_DGRAM;
-               alt_proto = 1;
        }
        else if (strncmp(str2, "tcp@", 4) == 0) {
                str2 += 4;
@@ -1129,7 +1129,6 @@ struct sockaddr_storage *str2sa_range(const char *str, int *port, int *low, int
                ss.ss_family = AF_UNSPEC;
                proto_type = PROTO_TYPE_DGRAM;
                ctrl_type = SOCK_DGRAM;
-               alt_proto = 1;
        }
        else if (strncmp(str2, "quic4@", 6) == 0) {
                str2 += 6;
@@ -1399,6 +1398,8 @@ struct sockaddr_storage *str2sa_range(const char *str, int *port, int *low, int
        }
 
        if (proto || (opts & PA_O_CONNECT)) {
+               // if the socket type is SOCK_DGRAM, use by default an alternate protocol
+               alt_proto = alt_proto || (ctrl_type == SOCK_DGRAM);
                /* Note: if the caller asks for a proto, we must find one,
                 * except if we inherit from a raw FD (family == AF_CUST_EXISTING_FD)
                 * orif we return with an fqdn that will resolve later,